ABSTRACTS of Oral

ABSTRACTS

Oral

S26 0.3 0.4 ENDOTHELIAL CELL ENZYMES: REGULATORS OF VASOACTIVE ALTERNATIVE PATHWAYS FOR ANGIOTENSIN II GENERATION IN MAN PEPTIDES Urata H and Arakawa K Fukuoka University, Dept. Internal Medicine 7-45-7 Nanakuma, Jonan-ku, Fukuoka 814-0180 Japan

Cl Johnston, Department of Medicine, The University of Melbourne, Austin & Repatriation Medical Centre, Melbourne, Australia The locally formed angiotensin (Ang) II play pathological roles in development of hypertensive heart disease, congestive heart failure, and acute myocardical infarction. The endothelial cell membrane contains 3 distinct peptidases important in This is substantiated by the fact that the introduction of angiotensin converting the production and metabolism of vasoactive peptides. Angiotensin enzyme (ACE) inhibitors and angiotensin II receptor antagonists improved the converting enzyme (ACE) is responsible for the production of angiotensin II mortality and morbidity of patients with various cardiovascular diseases as listed (ANGII), neutral endopeptidase (NEP) for the degradation of the above. One recent observation is the alternative pathway of Ang II formation by vasodilatory natriuretic peptides (NP), and endothelin converting enzyme serine proteases. So far, two types of angiotensin II-forrning serine proteases have (ECE) converts inactive big endothelin into the potent vasoconstrictor been identified: (I) aprotinin-sensitive or kallikrein type which forms bradykinin as endothelin. These 3 enzymes share many similarities; they are zinc well as angiotensin II, depending upon pH conditions: and (2) chymostatin-sensitive dependent cell surface ectopeptidases, their catalytic sites have high or the chymase type. The former system make some contribution to the regulation homology and they share many common substrates. Furthermore, the of tissue perfusion, as seen in the ischemic dog heart and the human leg. vasoconstrictors ANGII and endothelin are neuroexcitatory and stimulate At cell growth whereas NP's are neuroinhibitory and inhibit growth. These ischemic condition where the tissue pH decreases less than 7.0, kallikrein or tonin peptides produced locally by the endothelial cell may act in a paracrine or which are originally bradykinin-forming enzymes, turn to be Ang II-forming enzyme autocrine manner to provide acute local circulatory control as well as (Kinin-Tens in System). The latter enzyme, chyma,e, is widely distributed in structural cardiovascular remodelling. The mechanisms linking the activity various human tissues and is the most potent and specific Ang II-forrning enzyme in of these 3 enzymes are unknown but activation of these hormonal systems vitro. Recent studies provided the evidence that chyrna'e may participate in is involved in the pathophysiology of hypertension, left ventricular structural remodeling of heart and vessels: the tissue content of chyrnase significantly hypertrophy, heart failure and progression of renal failure. Although increased in atherosclerotic aorta and in the myocardium post acute myocardial blocking the RAS has been a significant advance in the treatment of infarction. Chymase appear to be involved in the metabolism of extracellular matrix cardiovascular disease, morbidity and mortality is still high. An additional proteins because it degrades some of them and activate the proform of tissue strategy would be to simultaneously inhibit combinations of these 3 destructive enzymes such as procollagenase and gelatinase. A recent report also important endothelial enzymes. Because of the similarity of their catalytic suggest that human chyrnase cleaves big endothelins to form endothelins ( 1-31 ), but site it has been possible to design compounds which act as dual or triple not ordinal endothelins (1-21), which are also biological active as ordinal endothelins peptidase inhibitors. These vasopeptidase inhibitors are now being studied These studies suggest that chyrnase may have other, as yet unknown, functions. in experimental cardiovascular models and some are undergoing early clinical studies.

0.5 0.6 How many angiotensin II receptors are there and do they have any Angiotensin II, Monocytes and Vascular Disease. clinical relevance? Carlos M Ferrario, MD, FACC. The Hypertension and Vascular Disease Center, Thomas Unger, M. D. Institute of Pharmacology, Christian-Albrechts-University Kiel, Wake Forest University School of Medicine. Winston-Salem, North Carolina Hospitalstr. 4, 24105 Kiel. Germany. 27157, USA In 1982, acid derivatives were issued, and it was soon recognized The pathophysiological continuum that begins with endothelial injury and that these compounds were capable of antagonizing ANG II-induced vasoconstriction in progresses to occlusive coronary artery disease is influenced by the association isolated vessels. This was the basis for the further development of highly specific and between hypertension and activation of the renin-angiotensin system (RAS). selective angiotensin ATl receptor binding substances such as losartan, valsartan, Recent clinical studies show that increased RAS activity is an independent risk irbesartan, candesartan, eprosartan, telmisartan, tasosartan and others. The availability factor for myocardial infarction, even after adjustment for other risk factors of these highly specific and selective ATl receptor antagonists was the basis for the including blood pressure, history of cardiovascular treatment or use of identification of the ANG II receptor subtypes. As of today, two main angiotensin Many of the effects of high blood pressure on the arterial wall are mediated by receptor subtypes have been characterized, ATl and AT2, which display a heterogeneous distribution in peripheral tissues and in the brain. In rodents, but not in humans, the ATl angiotensin II (Ang II). The vascular changes that occur at onset of the atherogenic receptor subtype exists in two isoforms, AT! a and AT! b. process are similar to those observed in the early phase of hypertensive vascular The AT! receptor belongs to the superfamily of7-transmembrane domain, G-protein disease, such as increased adherence of circulating monocytes and leukocytes to the coupled receptors and has an estimated molecular weight of65 kilodaltons. ANG II vascular endothelium, VSMC proliferation, and collagen deposition. Cellular and induced cell hypertrophy and hyperplasia are both mediated through the AT! receptor. molecular techniques have recently implicated a participation of the RAS in this In contrast to the ATl receptor, much less is known about the structural and functional process. In hypertensive [mRen-2]27 transgenic rats, chronic administration of properties of the AT2 receptor which is found ubiquitously and abundantly in fetal losartan but not hydralazine caused a substantial reduction in the number of tissues. In the adult organism, this receptor is present at high concentrations in the activated circulating and endothelium-adherent monocytes. The vasculo-protective

adrenal medulla, uterus and ovary and is also found in vascular endothelium and in effect of Ang II antagonism may not be solely related to inhibition of AT1 receptors distinct brain areas. The fact that the AT2 receptor is expressed at high levels in because both losartan and irbesartan behaved as competitive inhibitors of the

embryonic tissues but to a much lesser extent in normal adult tissues has raised thromboxane A2 receptor. speculations as to its possible role in development and cell differentiation. New studies in a primate model of atherosclerosis emphasize the importance of Although the AT2 receptor has been cloned recently, its molecular structure and signal Ang II in the mediation of atherogenesis. Male monkeys fed an atherogenic diet for transduction pathway are far from being completely understood. The rat AT2-receptor 20 weeks received a continuous infusion of losanan for the last six weeks of the eDNA encodes for a 363-arnino acid protein that has a seven transmembrane topology dietary regimen. This treatment caused a marked diminution of fatty streaks in the and a homology of32-34% in its amino acid sequence to the ATI-receptor. However, aorta and coronary arteries associated with a significant decrease in cholesterol it is still controversial whether or not the AT2 receptor is coupled to G-proteins, and content in the carotid and iliac arteries. These data suggest a direct role of Ang II in how it signals. The presence of different subtypes for the AT2 receptor as well as the the origin and evolution of plaque formation, a finding that is consistent with our existence of additional AT3 and AT 4 receptor subtypes are still controversially proposal that an activation of the vascular wall RAS may a prerequisite in the discussed matters. development of atherosclerosis.

S27 0.7 0.8 OPTIMAL DOSING CHARACTERISTICS CLINICAL PROFILE OF ANGIOTENSIN RECEPTOR BLOCKERS

Neutel J, Orange County Heart Institute, Orange, CA Meredith P, Gardiner Institute, Western Infirmary, Glasgow, Scotland

Evidence suggests that defining the appropriate dose and duration of action of an Poor control rates amongst hypertensive patients are perhaps the most significant antihypertensive drug is of paramount importance in the development of a new problem to be dealt with in the management of hypertension in the next milleonium hypertensive drug. From a historical perspective, it is apparent that on many occasiOns, Patient compliance with antihypertensive agents remains the most common cause of antihypertensives have been licensed at inappropriately large as result poor control rates and is dependent primarily on the side effect profiles of the drugs. of seeking to extend the duration of action such that the agent IS cons1dered smtable for Well-tolerated drugs, which are effective, are crucial in order to improve compliance once-daily administration. Subsequent dose reductions have agents rates. that do not have the desirable characteristics of a once-a-day antihypertensive. The introduction angiotensin receptor blockers has provided a very important Alternatively, the use of inappropriately high doses of drug may result in an alternative approach to the first-line management of hypertension. These drugs are unacceptable side-effect profile. extraordinarily well tolerated, and have a side-effect profile that has been shown to be Epidemiological evidence suggests that the benefits of antihypertensive therapy are better than that seen with placebo. In addition, newer generation angiotensin receptor likely to be maximised where blood pressure control is smooth and over the blockers such as telmisartan are extremely effective and have been shown in head-to full 24-hour period and this desirable characteristic has been acknowledged m the JNC head studies to have equal or slightly greater efficacy than other classes of VI guidelines. Thus, the aim should be to utilise agents with a well-defmed, dose antihypertensive agents including, diuretic, beta-blockers, calcium channel blockers and response relationship for both desirable and undesirable effects, and wtth a prolonged angiotensin converting enzyme inhibitors. Also, the newer generation angiotensin duration of action that offers a sustained antihypertensive effect. receptor blockers have prolonged half-lives and provide effective 24-hour blood Two characteristics of telmisartan can be considered to be desirable. Firstly, over the pressure control with once-a-day dosing. Moreover, animal studies and early human recommended dose range the antihypertensive effects of the drug have been well data have demonstrated that angiotensin receptor blockers, in addition to this blood defined, and over this dose range, the side-effect profile is comparable with that of pressure lowering effect, provide organ protection such as regression of left ventricular placebo. Secondly, telmisartan has a long half-life such that the combination of these hypertrophy and reduction in proteinuria. Angiotensin receptor blockers thus provide a two properties results in a prolonged duration of action, which is independent of dose. more complete package of efficacy, tolerability, convenience, and organ protection than The evidence for this can be supported not only by the trough:peak blood pressure data perhaps any other agent does. for telmisartan, which is consistently high over the recommended dose range, but also The selection of drugs that are effective and well tolerated will have a beneficial by comparison with alternative antihypertensives, particularly when focusing on the BP effect on blood pressure control rates and are thus likely to have impact on control in the final 6 hours of the dosing interval. cardiovascular outcomes in hypertensive patients. The importance of sustained and consistent blood control recognised. The evidence suggests that this is most appropnately ach1eved w1th antihypertensive agents with intrinsic, long duration of action.

0.9 0.10 Irbesartan reduces QT dispersion in hypertensives BLOOD PRESSURE AND RENAL EFFECTS OF INDOMETHACIN DURJNG TREATMENT WITH LOSARTAN. *Pitt 0 Lim, "'Marleen Nys, "'Abdul A 0 Naas *Allan D Struthers, -Mary Osbakken, and *Thomas M MacDonald, *Hypertension Research Centre, Department of Clinical Phannacology and ME.Olsen T Thomsen, C.Hassager, H!bsen, HDige-Petersen. Dept. Card. Therapeutics, University of Dundee, Ninewells Hospital and Medical School, Dundee DDl 9SY, Bispebjerg Hospital, Copenhagen. Dept. Int. Medicine and dept. Clin. Phys. Nucl. Unital Kingdom. "BMS, Waterloo, Belgium, ''BMS, Princetun NJ, USA. Medicine, Glostrup Amtssygehus, Copenhagen.

Non-steroid anti-inflammatory drugs have demonstrated an opposing effect on the We hypothesised that irbesartan, a specific AT1 receptor antagonist would reduce antihypertensive effect of angiotensin converting enzyme inhibitors. The present QT dispersion. In order to test this, we gathered ECG data from a multinational, study was undertaken to study if prostaglandin (PO) inhibition with indomethacin multicentre, randomised double-blind parallel group study that was designed to also interferes with angiotensin II receptor blockade during treatment for arterial compare the antihypertensive efficacy of irbesartan and amlodipine in elderly hypertension. subjects with seated diastolic BP 95 - 110 mmHg at the end of a 4-week placebo Ten patients with essential arterial hypertension, treated with losartan were run-in period. Subjects were treated for 24 weeks with either irbesartan 75-150 mg randomised to supplementary treatment with indomethacin (50 mg bid) or placebo or amlodipine 5-10 mg. Adjunctive therapy (hydrochlorothiazide and atenolol) was for one week. After a two week washout period, indomethacin/placebo treatment was allowed after 12 weeks if BP remained uncontrolled. Twelve-lead ECGs were crossed over. At the end of each treatment period with losartan plus obtained prior to randomisation and at the end of the study period. 188 subjects indomethacin/placebo, the following examinations were performed, preceded by four (118 with baseline ECGs) were randomized. We analysed 104 patients who had dayes sodium fixed diet (100 mmollday): 24 hour blood pressure (BP), 24 hour complete ECGs at baseline and after 24 weeks of treatment. The baseline sodium excretion (UN,V), supine BP, p-electrolytes, p-aldosterone, p-renin characteristics between treatment groups were similar apart from a slight imbalance concentration (PRC), p-atrial natriuretic peptide (ANP), glomerular filtration rate in DBP [Irbesartan 99.2 (3.6) mmHg vs Amlodipine 100.8 (3.8) mmHg, p 0.03]. (GFR), renal resistive indeks (RRI), extracellular volume (ECV) determination, There were no significant differences in blood pressure normalisation (DBP < 90 sodium clearance (CN,) and weight. mmHg) between treatment groups at 6 months [Irbesartan 80% vs Amlodipine 88%, Indomethacin did not significantly affect 24 hr BP nor supine BP. Indomethacin p=0.378]. We found a significant reduction in QT indices in the irbesartan treatment increased weight (p<0,05), and ECV (p<0,05). A not significant decrease in UN,V group [QTc dispersion, Mean -11.4 (SD 34.5) ms, QTc Max -12.8 (35.5) ms, p < was seen after indomethacin, as in 24 hr eN,. Conversely, in the laboratory eN, 0.05] and QTc dispersion did not correlate with the change in BP. Amlodipine did increased after indomethacin Indomethacin increased p-ANP (p

S28 0.11 0.12 ACTIVATED PERIPHERAL MONOCYTES IN ESSENTIAL HYPERTENSION EFFECT OF CANDESARTAN ON ENDOTHELIAL FUNCTION IN THE PERIPHERAL CIRCULATION OF ESSENTIAL HYPERTENSIVE PATIENTS. Y.Dorffel A.Hansen, Ch.Liitsch, B.Stuhlmiiller, G.R.Burmester, J.Scholze. L.Ghiadoni, A. Virdis, S. Taddei, A. Magagna, S. Vivaldi, M. Notari*, A. Salvetti. Outpatient Clinics oflntemal Medicine and Department ofRheumatology and Clinical Department of Internal Medicine, University of Pisa, Italy. * TAKEDA Italia Immunology, Charite University Hospital, Humboldt University, Luisenstrasse 11-13, rarmaceutici s.p.a. Rome, Italy 10117 Berlin, Germany Angiotensin II can impair endothelium-dependent (END) vasodilation (VD) by inducing· oxidative stress, which reduces NO availability, and increasing endothelin-1 The aim of this study was to investigate the possible involvement of human peripheral (ET-1) production. Since essential hypertensive patients (EH) are characterized by blood monocytes in the pathology of hypertensive disease. reduced END VD, in 15 EH (age 54±5 years; blood pressure (BP) 155±71104±4 We determined the in vitro secretion patterns ofproinflammatory cytokines from iso mmHg) we evaluated the effect of the new selective A Tl antagonist Candesartan lated peripheral monocytes from normal controls and hypertensive patients after in vitrc (CAN) on forearm blood flow (FBF, strain-gauge venous plethysmography) changes stimulation with angiotensin II with or without preincubation with the angiotensin II induced by the intrabrachial infusion of acetylcholine (ACH 0.1 5, 0.45, 1.5, 4.5, 15 subtype I receptor antagonist losartan. Blood samples were obtained from 22 patients 100 ml/min) an END vasodilator, in absence or presence of L-NMMA (100 with essential hypertension before any drug administration or after interruption of the [lg/100 ml!min) an NO synthase inhibitor; TAK-044 (TAK: 10, 30, 100 antihypertensive therapy and from 24 normotensive healthy individuals as a control ml!min), an antagonist for ET-A and ET-B receptors; sodium nitroprusside (SNP: I, 2, group matched for sex and age. Peripheral blood monocytes were isolated by density 4 [lg/100 mllmin), an endothelium-independent vasodilator, and noradrenaline (NA: gradtent centnfugatwn and plasttc adherence. The state of monocyte activity was de 0.003, 0.009, 0.03 [lg/100 mllmin). Infusions were repeated after 2 month oral termined by the capacity to secrete interleukin Ill (IL-113), tumor necrosis factor a. treatment with CAN (8 mg/daily). I 0 matched normotensive controls (NT: age 51±6 (TNF-a.), and interleukin 6 (IL-6) either spontaneously or after stimulation with angio years; BP 121±4178±3 mmHg) were also evaluated. EH showed a reduced (* p

0.13 0.14 LOSARTAN REDUCES ASYMPTOMATIC VENTRICULAR ARRHYTHMIAS IN ADDITIVE EFFECTS OF LOSARTAN + ENALAPR!L IN THE REDUCTION OF MILD HYPERTENSIVE PATIENTS LEFT VENTRJCULAR HYPERTROPHY IN HYPERTENSIVE PATIENTS.

Massjmo Crlpoa, Glanpaolo Damiani, llarla Notaristelano, Raffaella Costa, A.C. Avanza, L.M. El Aouar, J.G. Mill. Biomedical Center, Federal University of Ermanna Chlari, Raffaele Fariello Espirito Santo, Viloria, 29040-090 Brazil. Opts lnt Med & Cardiol, Spedali Civil!, Brescia, Italy Left ventricular hypertrophy (LVH) is an important risk factor for hypertensive Asymptomatic ventricular arrhythmias are often seen in uncomplicated patients. Thus, reduction of L VH must be an essential goal in treatment of high blood essential hypertensive patients. We evaluated the effect of losartan, 25 to 50 pressure (BP). ACE inhibitors and angiotensin II-AT antagonists are currently used as mg o.d. for a 4-month period in 10 patients (8 males- 2 females, aged 28 to 70 1 isolated drugs in such conditions. Since angiotensin II is generated by multiple years, mean 45.2) with mild and uncomplicated essential hypertension without antihypertensive treatment. Twenty-four-hour ECG monitoring (FukudaDenshi enzymatic pathways and the antihypertrophic effect of ACE inhibitors may also depend SM-40) was carried out alter a two-week placebo period and at the end of on bradykinin, we compared the reversion ofLVH in hypertension with enalapril (Ena), active losartan treatment. Results: losartan (Los) or associating these drugs at reduced doses. RELATIONSHIP BETWEEN BP & ARRHYlHMIAS Patients of both sexes (N=6l , 40-50 y) with moderate hypertension (24-h ambulatory blood pressure monitoring) and L VH continned by echocardiography (left ventricular mass index, L VMI: males> 130 g/m2; females> I 10 g/m2) were divided into three groups treated with Ena (35 mg/day), Los (175 mg/day) or the Ena+Los (15 mg+ ! OO mg/day). Forty six patients completed the 10 month treatment (Ena:l5; Los:15; Ena+Los:16). BP decreased similarly in all groups. All treatments were also effective (P

potassium.

S29 0.15 0.16

ANGIOTENSIN AT, RECEPTOR (AT1R) BLOCKADE MEDIATES A RENAL CHRONIC AT, BLOCKADE WITH !RBESARTAN PREVENTS NADPH/NADH BRADYKININ (BK)-NITRIC OXIDE (NO) CASCADE OXIDASE OVEREXPRESSION IN THE AORTA OF SHR

H.M. Siragy, M. de Gasparo, R.M. Carey. Department of Medicine, G Zalba, J Beaumont, A Fortuilo, JC Etayo, S Ravassa, MA Fortufto, J Diez. University of Virginia, Charlottesville, VA and Novartis Pharma Basel Vascular Pathophysiology Unit, University ofNavarra, Pamplona, Spain. Switzerland. ' '

We hypothesized that AT1R blockade is associated with increased An association of endothelial dysfunction with enhanced production of superoxide production of renal NO through release of BK. Utilizing a microdialysis anion (-02") has been reported in the aorta of adult SHR. Recently, it has been technique, we monitored changes in renal interstitial fluid (RIF) BK, nitrate shov.n that angiotensin II induces -02· production in animals made hypertensive by (NOX) and cGMP in response to i.v. infusion of the AT1R blocker Valsartan infusion of the peptide, by upregulating expression of p22phox, a component of the (V) (10 mg/kg) or BK B, receptor blocker, icatibant (I) (10 in NADPHINADH oxidase system. To gain insight into the mechanisms of conscious rats (N=10) during low Na intake. RIF BK, NOX and cGMP endothelial dysfunction in arterial hypertension we investigated the expression of increased (P<0.001) during (V) treatment from 3.6 ± 0.03 to 8.5 ± 0.16 p22phox messenger Rl'IA in the aorta of 30-week-old normotensive Wistar-Kyoto 1 ng/min, 0.28 ± 0.01 to 0.39 ± 0.01 and 0.9 ± 0.01 to 1.7 ± 0.03 rats (WKY), SHR and SHR treated with irbesartan (20 mg. Kg·'. d' ) during 14 pmol/min, respectively. During (I) infusion, RIF NOX and cGMP decreased weeks before sacrifice. The expression of p22phox mRNA was assessed by by 64% and 40% (P<0.001 ), respectively, while BK increased (P<0.01 ). competitive RT-PCR. Endothelium-dependent relaxations were analyzed in Combined administration of (V) and (I) prevented the increase in RIF norepinephrine-precontracted rings exposed to Ach. As compared to WKY, cGMP and NOX associated with (V) alone and increased BK (P<0.001 ). untreated SHR exhibited increased (P

0.17 0.18 TREATMENT WITH LOSARTAN ENHANCES THE SELECTIVITY OF THE IMPLICATION OF ANGIOTENSIN II IN THE EXPRESSION OF Na•-Hc0-3 SYMPORTER AND Na•-H• EXCHANGER IN RAT MYOCARDIUM AFTER SARCOLEMMAL Na•-K• PUMP FOR Na• VIA PROTEIN KINASE C. MYOCARDIAL INFARCTION K.A. Buhagiar, P.S. Hansen and H.H. Rasmussen. Department of Cardiology. MH. Yu, S. Sandmann, Th. Unger. Institute of Pharmacology, University of Royal North Shore Hospital, Sydney, Australia. Kiel, and German Institute for High Blood Pressure Research, Heidelberg, Germany. Treatment of rabbits with the AT 1 receptor antagonist losartan (los) increases The cardiac tissue RAS is activated, and that both AT1 and AT2 receptors are the affinity of the Na • -K• pump for intracellular Na • (Hoot LC et at , Am. J. upregulated in the myocardium during the early phase after myocardial Physiol. 1996; 271 :C 17 2-180). This is due to an increase in the selectivity infarction (MI). Genes that might be regulated by ANG II include the Na·• for Na • over K • at intracellular sites (Buhagiar KA et al, J . Hypertension HC0-3 symporter and Na•-H• exchanger which contribute to recovery from 1998; 16(Suppi.2):S124). Since many effects of angiotensin mediated intrcellular acidosis in cardiac tissue. We therefore investigated the influence through the AT, receptor are thought to involve PKC, we speculated that of ANGII on the Na•-Hco·3 symporter and Na•-H• exchanger mRNA PKC may be involved in this effect of los treatment. Myocytes isolated from expression in rats during the acute phase following ligation of the left anterior control rabbits and from rabbits treated with los for 8 days were patch descending coronary artery. Rats were sacrificed 1d, 3d, 7d and 14d after clamped with wide-tipped pipettes. This allows control of membrane voltage Ml or sham operation. RNA from the left ventricular free wall including and the chemical composition of the intracellular compartment and it enables infarcted tissue and area of risk was extracted. The mRNA expression was measurement of whole-cell membrane current s. Pipette filling solutions determined by RT-PCR and RNase protection assay. The house keeping included 10 mM Na• and either 0 or 70 mM K• tK•,l. In some experi ments gene, GAPDH mRNA, was used as an internal standard. Both Na•-Hco-3 filling solutions also contained the specific PKC-activating peptide (PKC-PI. symporter and Na•-H• exchanger mRNA expression was increased after MI. Na • -K • pump current (I•) was identified as the shift in current induced by The peak point of Na+-HC03- symporter expression was at 14 days; of the pump blockade with 100 pM ouabain. Mean t; s ( ± SE) in myocytes from Na• -H· exchanger was at 7 days. The ACE inhibitor (ramipril 1 mg /kg/day) control rabbits and los treated rabbits were similar when K• ; was 0 mM. In contrast, when K•; was 70 mM, los induced a significant increase in '• substantially reduced the Na • -H• exchanger and Na• -HC03- symporter compared to controls (see f1gure, expression. The angiotensin AT2 receptor antagonist (PD 123319 30 *p < 0.05). Dialysis of myocytes 1.2 mg/kg/day) reduced the Na• -HC03- symporter expression, but had no effect I 0 mM K•; I on Na• -H• exchanger expression. from los treated rabbits with filling 1.0 solutions containing the PKC-P Our findings indicate that the mRNA of the Na•-Hco-3 symporter and Na•-H• eliminated the effect of los when exchanger are elevated in heart tissue of the acute phase of MI. The K•; was 70 mM, but had no effect l: upregulation of Na•-HC03 symporter expression is mediated at least in part - " .4 when K+; was 0 mM. Thus, the by the AT2 receptor. The results further suggest that transcriptional los-induced increase in the .2 regulation significantly contributes to the control of the pH regulatory systems selectivity of the pump for Na • is in cardiac tissue pointing to possible role of AT receptor in the intracellular 2 likely to involve PKC. pH regulation after MI.

S30 0.19 0.20 AT1- AND AT2-RECEPTORS ARE INVOLVED IN NORADRENALINE ANGIOTENSIN IT INDUCES SUPEROXIDE ANION PRODUCI'ION BY RELEASE IN HUMAN ATRIA. MESANGIAL CELLS VIA ATl RECEPTORS

L. C. Rump, E. Schwertfeger, V. Oberhauser. Dept. of Nephrology, E.A. Jaimes, J.M. Galceran and L. Raij. VA Medical Center, One Veterans Drive and University of Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany Univ. of Minn. School of Medicine, Minneapolis, MN 55417 USA.

Angiotensin II (Ang II) mediates its effects through AT1- and AT2 receptors, The recognized role of angiotensin II (Ang II) in the pathogenesis of the both of which are present in human atrium. AT1-receptor activation in• progression of renal disease cannot be solely attributed to Ang II's hemodynamic creases noradrenaline (NA) release ,Rump, Lancet 1998, 351: 644-5" effects. Indeed, growth stimulating signals driven by Ang II promote mesangial cell (MC) hypertrophy and extracellular matrix production, prominent features of whereas the role of AT2 receptors, representing about 75% of Ang II recep• progressive glomerular injury. Superoxide anion (Oz-) avidly interacts with nitric tor sites in the heart, is unclear. We investigated AT1 and AT2 receptor me• oxide, an endogenous vasodilator that inhibits growth factor stimulated MC growth diated effects on NA and acetylcholine (ACh) release in human atria in vitro. and matrix production. In addition, az- acting as an intracellular signal is linked to Atria were loaded with 3H-NA or 3H-hemicholine. The cardiac nerves were growth related responses such as activation of mitogen activated protein (MAP) stimulated electrically at 5 Hz. The effect of Ang II, the AT1 receptor blocker kinases. The studies reported herein were designed to investigate: (a) whether Ang II EXP3174, the AT2 receptor blockers PD123319 and CGP42112A were induces MC Oz- production and (b) if increased Oz- production elicits growth tested at different concentrations. responses in MC. MC were exposed to Ang II for 24 or 48 hours. In some experiments, in addition ANG II (0.001-0.1 increased NA release. The dose response curve of to Ang II, MC were exposed to: diphenylenieodonium (DPI), an inhibitor of the Ang II was shifted to the right by EXP3174 (0.01 The AT2-receptor flavin containing NADH/NADPH oxidase; losanan (LOS), an Ang II type 1 (ATl) blockers PD123319 (1 and CGP42112A (1 reduced the Ang II in• receptor blocker; PD 98059, a MAP kinases inhibitor; the protein kinase C inhibitors duced increase of NA by 50 %over the whole concentration range of Ang II. Calphostin Cor H-7; and the tyrosine kinase inhibitors, herbymycin A or genistein. Such an inhibition with PD123319 was not observed previously in renal Ang II (1Q·5 M to lQ-8 M) dose dependently increased MC Qz- production up to cortex ,Rump, Hypertension 1995, 26:445-51", a tissue lacking cholinergic 125% above control (ED 50 5 X lQ-7 M). LOS as well as DPI, and the protein innervation. The combination EXP3174 I PD123319 did not inhibit NA re• kinase C inhibitors blocked Ang II stimulated MC 02- production. Ang II dose lease to a greater extent than EXP3174 alone. ACh release was increased dependently increased MC 3 H-leucine incorporation, and MC protein content, two by Ang II (0.01-1 This effect was inhibited by EXP3174 (0.1 markers of MC hypertrophy, as well as 3H-thymidine incorporation, a marker of MC In conclusion, Ang II increases NA outflow in the human atria by activation hyperplasia. PD98059, a specific inhibitor of MAP kinases prevented Ang IT induced MC hypertrophy. Moreover, LOS, DPI, and the protein kinase C inhibitors each of presynaptic A T1-receptors on sympathetic nerve endings. The inhibitory independently inhibited MC 3H-leucine incorporation, thereby establishing the effect of AT2-blockers on NA release is unclear at present but may involve specificity of Ang IT induced Oz- in driving MC hypertrophy. an effect of Ang II on ACh release. We hypothetize that activation of AT1 The current studies demonstrate a previously unrecognized link between Ang II receptors enhances and activation of AT2 receptors inhibits ACh release. and MC az- production that may participate in the pathophysiology of progressive Blockade of AT2 receptors thus leads to enhanced ACh release and activa• renal disease by concomitantly affecting the hemodynamics of the glomerular tion of inhibitory muscarinic receptors on noradrenergic nerve endings. microcirculation as well as growth related responses of MC to injury.

0.21 0.22 Comparative effects of ACE inhibition and A-ll antagonism on the neurohormonal ACE inhibitors and A-II antagonists in the management of hypertension modulators of blood pressure Professor Domenic Sica, Medical College of Virginia of Virginia Commonwealth Hans Brunner, Hospital Nestle, Lausanne, Switzerland University, Richmond, USA Interruption of the renin-angiotensin axis (RAA) has become an increasingly attractive target in the management of hypertension and/or end-organ disease. The Angiotensin II (A-II) receptor antagonists and angiotensin-converting pharmacological manipulation of this axis has been accomplished with a broad range of enzyme inhibitors (ACEis) are both now recognised for the treatment drug classes, including 13-blockers, angiotensin-converting enzyme inhibitors (ACEis), of hypertension. Although both drug classes affect the renin-angiotensin and most recently angiotensin-receptor antagonists (AT 1-RAs). However, the latter two system (RAS), important differences differentiate the two drug classes. drug classes have been most frequently employed. ACE inhibition and angiotensin A number of studies have investigated efficacy and dose-response issues receptor blockade are fundamentally different means by which the RAA may be of these agents and key findings will be reviewed in this presentation. interrupted. In the latter instance, the AT,-receptor is blocked either in a competitive or In particular, it will be demonstrated that the recommended starting doses non-competitive (insurmountable) fashion, while in the former, the production of angiotensin-II is interrupted. ACEis are further distinguished from AT,-RAs by their of some A-II receptor antagonists produce quite different levels of ability to inhibit bradykinin metabolism, since the ACE enzyme is involved in the blockade of the RAS, both at peak as well as at trough. Taken together, degradation of bradykinin. Such an alteration has recently been invoked to explain how ACEis as well as A-II antagonists, when dosed correctly, are extremely ACEis reduce blood pressure, since angiotensin-II concentrations return to normal levels efficacious antihypertensive agents, equally effective in reducing (so-called 'angiotensin-escape') with chronic dosing. Angiotensin-II levels also increase systolic as well as diastolic blood pressure. A-II antagonists have with AT,-RA administration, but in an innocuous fashion. Blockade at the AT,-receptor the additional advantage that so far no class-specific side-effect is known. interrupts a short feedback loop, with resultant increases in upstream components of the RAA. Angiotensin-II concentrations may rise several-fold in concert with AT ,-receptor blockade. The AT 1-receptor is well protected from such rises in angiotensin though, the AT 2-receptor is actively stimulated. The true import of the AT ,-receptor remains to be determined. A final differentiating feature between ACEis and AT,-RAs relates to the influence of each treatment modality on sympathetic nervous activity. Therein, ACE inhibition has typically resulted in no or minimal change in catecholamine concentrations, though the disease being studied influences the observed results. AT,-RAs more consistently decrease catecholamine concentrations, with recent observations suggesting that a more prominent effect occurs with the AT ,-RA, eprosartan.

S31 0.23 0.24 The role of RAS blockade in reducing cardiac and renal disease risk REACTIVATION OF THE RENIN ANGIOTENSIN SYSTEM DESPITE Dr Luis M Ruilope, Hospital I 2 de OchJbre, Madrid, Spain Cardiac and renal risk usually run in parallel. Left ventricular hypertrophy (LVH) and ACE INHI'IHTI ON myocardial ischaemia are frequently accompanied by hyperfiltration and/or Allan D Struthers microalbuminuria. Chronic renal failure is characterized by a higher prevalence of L VH, Department of Clinical Pharmacology & Therapeutics heart failure and myocardial infarction (MI). For these reasons, pharmacological Ninewells Hospital, Dundee, DOl 9SY. treatment of arterial hypertension must contemplate both cardiac and renal protection simultaneously. Blockade of the effects of angiotensin IT (A-II) on the cardiovascular and renal systems has proven to be of great value to patients suffering from arterial hypertension, heart failure, MI, L VH and chronic renal failure. This was demonstrated with the utilization of angiotensin-converting enzyme (ACE) inhibitors and has It is now clear that the renin angiotensin aldosterone system (RAAS) does accounted for their wide prescription. However, diminution of the cardiovascular and not remain fully suppressed by conventional ACE inhibition. There are renal risk achieved through the administration of ACE inhibitors has not surpassed 50%. three separate aspects to RAAS activation: firstly reactivation of plasma For this reason, any new mechanism of action by which to block the effects of A-II that All, secondly reactivation of plasma aldosterone and thirdly reactivation may thereby further reduce the risk of cardiovascular and renal disease has to be very of vascular ACE. Little is yet known about why these occur and how welcome. commonly. The A-Il-receptor blockers constitute a new class of antihypertensive drugs that inhibit the binding of angiotensin to the A-II type I (AT,) receptor. Pharmacological and We recently examined 91 routine patients with chronic heart failure, all on preclinical studies indicate that this new class of drugs blocks the actions of A-II to a greater degree than previously available antihypertensive agents. In addition, the A-Il standard ACE inhibitor therapy. Plasma All reactivation occurred in 15% receptor antagonist eprosartan has been shown to have a higher capacity to vasodilate of patients and plasma aldosterone in 38% of patients. In half of those the kidney than previous drugs. Such clinical data, and the possibility that this class of with plasma All reactivation, serum ACE was also elevated, suggesting drugs may have a greater capacity to decrease mortality due to heart failure, indicate that that poor compliance or inadequate dosing with ACEJs was a factor. they could achieve more of an improvement in the outcome of patients compared with In a separate study, we assessed vascular ACE activity by the differential ACE inhibitors. Furthermore, the best tolerability ever experienced with an infusion of AI and All in CHF patients. Vascular ACE was greater in antihypertensive drug has been with A-ll-receptor blockers. Considering that blockade of NYHA class III vs class 1/Il and was greater with low dose ACEI vs high the renin- angiotensin system (RAS) is now employed in 25- 50% of the hypertensive population, the excellent tolerability and good profile in cardiovascular and renal dose ACE!. protection displayed by this class will greatly facilitate our decision to use a drug like eprosartan for the treatment of cardiovascular and renal disease. In conclusion, vascular ACE reactivates as the heart failure disease process progresses and this effect occurs even when patients are fully compliant with their ACEI therapy.

0.25 0.26 PHARMACOKINETICS AND PHARMACODYNAMICS OF ANGIOTENSIN IJ Efficacy of Angiotensin D Antagonists: A Comparative Analysis ANTAGONISTS Bryan Williams, MD FRCP, Professor of Medicine, Cardiovascular Research Institute, Faculty of Medicine & Biological Sciences, University ofLeicester, UK Michel Azizi, Joel Menard. Centre d'Tnvestigations Cliniqucs 9201, AP-HP/INSERM, H6pital Broussais, Paris, France. Angiotensin II antagonists (AliAs) have become established as effective and Angiotensin II antagonists dose-dependently decrease blood pressure in hypertensive patients seemingly well tolerated antihypertensive monotherapy. Currently four different and in sodium-depleted normal subjects, block the pressure response to exogenous ArrAs are available in clinical practice; candesartan, irbesartan, losartan and angiotensin II in healthy subjects, increase plasma renin and endogenous angiotensin Jl levels valsartan and more are likely to become available. Differentiating within the class and increase renal blood flow without modifying glomerular filtration rate. These antagonists has become an intense area of debate with particular controversy surrounding share with the first-marketed compound, losartan, and its active metabolite EXP-3174 the reported differences in antihypertensive efficacy between different agents within specificity of their binding to the AT! receptor, but they have different I) affinity constants, the AliA class. Review of the US-FDA regulatory review data reveals that the especially dissociation kinetics from the receptor, which affects the in vivo potency, 2) placebo-corrected reductions in trough diastolic blood pressure (DBP) for AliA antagonism characteristics (competitive or insurmountable), and 3) in vivo pharmacokinetics monotherapy in 7,339 patients receiving recommended therapeutic doses of (bioavailability, distribution, metabolism and elimination). The initial activity of the renin AliA were; candesartan, 4-8 mmHg; irbesartan, 5-8 mmHg; losartan, 3.5-7.5 angiotensin system has a fundamental influence on the antihypertensive response to an angiotensin II antagonist-based treatment. The more active that system, the stronger the mmHg; valsartan, 3-5 mmHg. Similar equivalence in response across the ATIA antihypertensive response. Thus, therapeutic outcome may be optimised by targeting class was observed for systolic BP reduction. A second data set using pooled angiotensin 11 antagonists to patients whose renin angiotensin system is not at rest, or by using data from 43 randomised clinical trials (11,281 patients) also revealed comparable angiotensin II antagonists with superior efficacy to losartan. Undoubtedly, it is possible to weighted average BP reductions (not placebo-corrected) for ATIA monotherapy. improve the pharmacokinetic and pharmacodynamic properties of angiotensin II antagonists. Patient responder rates for starting doses of ArrAs were equivalent across the Nevertheless, it remains very difficult to demonstrate a clinically significant superior effect. class at SO%, and monotherapy dose titration achieved a 55% responder rate. In addition to pharmacological potency, which depends on receptor affinity, the 21 randomised controlled trials comparing AliAs to other classes of therapy pharmacokinetics of the drug should pennit greater consistency between patients in the degree (ACE-Inhibitors, Calcium channel blockers and thiazide diuretics) also suggests of receptor binding of the antagonist. Phannacokinetic studies combined with pannacodynamic studies arc therefore especially necessary. If inter-individual comparable antihypertensive efficacy at equipotent doses. After failure of phannacokinetic variability is reduced, the variability of the pharmacodynamic response may monotherapy, titration to starting doses of AIIA/hydrochlorthiazide combinations also be reduced. It is possible to find drug doses that provide a genuinely constant level of produced 70% response rates. This therapeutic combination appears to be more antihypertensive effect over a 24-h period, without fluctuations and that reflect placebo effective than monotherapy dose titration. This analysis of published data and corrected trough/peak ratios close to one. With such an activity profile, wholly maintained regulatory review data suggests that the ArrAs show equivalent antihypertensive over 24 h, the consequences of forgetting a dose 24-h after the last drug intake are minimised. efficacy and response rates to each other (and other classes of antihypertensive ln humans, certain experimental models allow quantification of the relative effects of therapy) when used at their recommended dose in monotherapy. different inhibitors on the renin angiotensin system. It is possible to determine which agents are the most effective in tenns of blocking the renin angiotensin system over a 24-h period.

S32 0.27 0.28 OVERVIEW OF OUTCOME TRIALS WITH ANGIOTENSIN II ANTAGONISTS-WHAT'S NEW INSIGHTS INTO THE MECHANISM OF ACTION OF ANGIOTENSIN II RECEPTOR BLOCKERS NEEDED? H Siran lntemal University of Virginia Health Sciences Center, Charlottesvtlle, USA The renin-angiotensin system (RASJ plays an important role in regulation of body water, electrolyte homeostasis B Neal, S MacMahon. Clinical Trials Research Unit, University of Auckland, Private Bag 92019, and blood pressure control. Previous studies have linked the increased activity of the RAS to the development of Auckland, New Zealand cardiovascular diseases and hypertension in particular. Thus, efforts have been directed towards limiting the formation and activity of angiotensin II, the most active hormone of this system. The knowledge that angiotensin During the last decade there has been an unprecedented rise in the number of large scale randomised trials ll is formed through a classic pathway involving angiotensin-converting enzymes (ACE) has led to development of investigating the effects of antihypertensive agents on cardiovascular morbidity and mortality. In most of inhibitors of this enzyme. However, other pathways have been identified that can lead to formation of angiotensin these tria1s the study drug is a calcium antagonist or an angiotensin converting enzyme inhibitor but II independent of ACE. This has been confirmed by the detection of significant amounts of angiotensin II in several studies include participants randomised to angiotensin II antagonists (.AIIAs). A registry of major individuals who are being treated with ACE inhibitors lACEis). ongoing or planned randomised trials of antihypertensive agents has been established by the WHO-ISH In humans, two angiotensin receptor subtypes, AT 1 and AT 2, have been identified, cloned, sequenced and their Blood Pressure Lowering Treatment Trialists' Collaborative Group. The aims of this Group include the pharmacological properties identified. Most of the known functions of angiotensin II are mediated by AT1 conduct of meta-analyses of trials comparing the effects of (1) newer versus older classes of blood pressure receptors whereas functions for AT z receptors are still emerging. AT 1 receptors are distributed over the body and lowering drugs in patients with hypertension; and (2) newer blood pressure lowering drugs versus have specific functions that are dependent on their location. The best well-known functions for AT t receptors are untreated or less treated control conditions in various patient groups at high risk of cardiovascular events. The principal outcomes are stroke, major coronary heart disease events and total cardiovascular events. A related to vasoconstriction, hypertrophy and proliferation. Thus, angiotensin II receptor blockers are not only total of 38 trials of blood pressure lowering treatments scheduled to enroll about 270,000 participants have vasodilatory drugs but also affect cell proliferation. In contrast to the ATt receptor, ATz receptor stimulation has been confirmed as eligible for inclusion. Five trials involving aOOut 31,000 participants include been linked to vasodilation, nitric oxide release, apoptosis and antiproliferation. Blockade of the ATt receptor is comparisons of an AliA versus another active regimen and/or placebo. These studies will provide accompanied by an increase in plasma levels of angiotensin II, and may benefit stimulation of the AT2 receptor, information aOOut moderate differences in the effects of AliAs compared to calcium antagonists or beta which is unblocked. blockers on major cardiovascular events in patients with hypertension. In addition the studies will provide Based on the mechanism of action, similarities and differences exist between angiotensin II receptor blockers and information about the effects of AliAs on renal and cognitive outcomes in high risk groups. Future ACEis. In the kidney, angiotensin receptor blockers affect the glomerular haemodynamics less than ACEis and studies of AliAs might usefully examine the effects of these agents in alternate settings, such as other high may be more beneficial in patients with renal hypoperfusion. In diabetic rats, acute treatment with valsartan, an risk nonnotensives, acute stroke patients or as additional therapy among patients prescribed other classes angiotensin II receptor blocker, reduced proteinuria to the same extent as ACEis. Treatment with of antihypertensive drug. haemodynamically equally effective doses of an ACEI, or an angiotensin ATt receptor blocker, reduced to the same extent the area of the intima after balloon injury in spontaneously hypertensive rats. Both drugs decreased smooth muscle cell migration, but only angiotensin receptor blockers inhibited smooth IT'llscle cell proliferation. In contrast to ACEis, angiotensin receptor blockers did not decrease striated muscle microcirculation in spontaneously hypertensive rats and did not therefore enhance microresistance despite similar effects on blood pressure. Finally, because the AT2 receptor is stimulated during ATt receptor blockade and not by ACEis, ATt receptor blockade may have a greater advantage in vascular and cardiac remodelling and a greater renal protective effect.

0.29 0.30 THE CLINICAL BENEFITS OF ANGIOTENSIN II RECEPTOR BLOCKERS: PROVEN ADVANTAGES AND LONG-TERM EFFECTS OF ANGIOTENSIN II RECEPTOR BLOCKERS ON CARDIOVASCULAR MORBIDITY ONGOING CLINICAL TRIALS AND MORTALITY: THE VALUE TRIAL Thomas MacOonal

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