Renin-Angiotensin-Aldosterone System in Essential Hypertension

Br. J. clin. Pharmac. (1981), 12. 387-392

EFFECT OF CHRONIC DIURETIC TREATMENT ON THE PLASMA RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM IN ESSENTIAL HYPERTENSION

P. LIJNEN, R. FAGARD, J. STAESSEN & A. AMERY Hypertension and Cardiovascular Rehabilitation Unit, Department of Pathophysiology, University of Leuven (K.U. Leuven), Belgium

1 Chronic treatment with a constant dose of hydrochlorothiazide or tienilic acid increases plasma renin activity (PRA) acutely to reach a maximum within the first week. 2 During chronic diuretic therapy from 1 month to 1 year, PRA remained elevated at a rather constant level, though this was somewhat lower than the maximum level reached after 1 week. 3 A significant (P< 0.01) correlation (r= 0.74) between changes in plasma angiotensin II and renin activity provoked by chronic treatment for 3 months with hydrochlorothiazide and tienilic acid was found. 4 The increase in plasma aldosterone during chronic treatment with hydrochlorothiazide and tienilic acid (1000 mg) is related (r= 0.68; P< 0.01) to the rise in plasma angiotensin II.

Introduction In acute studies the diuretic-induced volume contrac- had been explained to them. The study complied with tion causes increases in plasma renin activity the code of ethics of WHO for human experimenta- (Hayduk et al., 1974; Wallach, Nyarai & Dawson, tion (Declaration of Helsinki). 1975). Whether this hyperreninemia is sustained All antihypertensive treatment had previously during chronic diuretic treatment remained however been interrupted for at least 4 weeks. During an unsettled since some authors reported a persistent initial run-in period on placebo for 4 weeks the pa- elevation (Laragh, 1973; Morganti et al., 1979; Van tients had laboratory studies including haemogram, Brummelen, Man In 't Veld & Schalekamp, 1980) urinanalysis, fasting blood sugar, serum creatinine, while others found only a transient one (Bourgoignie, electrolytes, bilirubin, plasma renin and aldosterone, Catanzaro & Perry, 1968; Sambhi et al., 1976; Max- urinary catecholamines, electrocardiogram, pulmo- well & Gross, 1979). nary function tests and chest X-ray. We have therefore investigated this further by All patients previously had an intravenous pyelo- studying the effect of chronic treatment with hydro- gram and some a renal arteriogram if indicated. chlorothiazide on plasma renin, angiotensin I and II Patients with any of the following were excluded and aldosterone levels in hypertensive patients. The from the study: signs of heart failure, haematological, effect of hydrochlorothiazide was also compared with hepatic or nonhypertensive cardiac disease, possibili- tienilic acid (2,3-dichloro-4(2-thienyl-carbonyl) ty of pregnancy by history, a recent cerebrovascular phenoxy acetic acid), a diuretic with powerful accident, a creatinine clearance below 30mlmin-', uricosuric properties whose major site of diuretic diabetics on insulin or oral hypoglycaemics, serum action is thought to be in the distal tubule (Stote, potassium below 3.4 mEq or serum uric acid Cherrill & Erb, 1974). > 10 mg% or history of gout. Procedures Methods All patients (n= 14) were first treated with two Subjects placebo tablets (at breakfast) daily for 1 month. They then entered a double-blind study where in group A Fourteen patients with essential hypertension were (n= 5) a fixed dose of tienilic acid (250 mg), in group selected for this study. Informed consent was ob- B (n= 5) a weekly doubling dose of hydro- tained after the nature of the test and the procedures chlorothiazide (25, 50 and 100 mg) and in group C 0306-5251/81/090387-0)6 $01.0) ©) Macmillan Publishers Ltd 1981 388 P. LIJNEN, R. FAGARD, J. STAESSEN & A. AMERY

(n=4) tienilic acid (250, 500 and 1000mg) was Table 1 General characteristics of the patients administered. The patients were seen at the out- Total number (n) 14 patient clinic after overnight fasting at weekly inter- Sex: males (n) 8 vals during the run-in period on placebo and during females (n) 6 the first month of active treatment and later every 4 Age (years) 37.2 ± 2.7* weeks and then every 8 weeks. Blood for assay of the Body weight (kg) 77.2±2.2 biochemical variables was drawn from an antecubital Blood pressure (mm Hg)t 169.9±4.3 vein around 11.00 h after the patient had been sitting in an relaxing arm-chair for 15 min. They had taken 99.9± 3.0 their morning dose. Creatinine clearance (ml/min) 124.1 ±6.6 WHO classification of hypertension Methods of measurement stage I 10 stage II 4 The plasma renin activity (PRA) was measured by Eye fundus, grade according to radioimmunoassay of the angiotensin I generated Keith-Wagener: during a 1 h incubation of the plasma samples with grade 0 5 the endogenous renin substrate at pH 6.0 and at 37°C grade 1 4 according to the method of Fyhrquist & Puutula grade 2 5 (1978). PRA was measured in plasma samples im- Electrocardiogram: normal 13 mediately after thawing and after storage of the left venticular 1 plasma at -5°C at pH 7.4 for 4 days. The value of hypertrophy PRA before and after exposure of the plasma to the cold is referred as active (APRA) and total plasma * Mean ± s.e.mean is given renin activity (TRPA). The difference (TPRA- tBlood pressure measured, during the run-in period on APRA) is taken as inactive plasma renin activity placebo, in recumbent position at the out-patient clinic. (IPRA). A radioimmunoassay method was used for the measurement of the endogenous plasma angiotensin 1. Changes in PRA during the first 3 weeks oftienilic I and II concentration (PA I, PA II) and of plasma acid treatment aldosterone concentration as previously described (Lijnen, Amery & Fagard, 1978; Lijnen et al., 1978; In the five patients of group A treated from the start Lijnen etal., 1978). and continuously with 250 mg daily tienilic acid, Plasma angiotensin converting enzyme (kininase PRA was increased within 1 week and did not show II) activity (ACE) was measured spectrophotometri- any further rise (Figure 1). There was a tendency of cally as described (Lijnen & Amery, 1978). levelling-off during the second and third week after Plasma noradrenaline, adrenaline and dopamine an initial rise during the first week. were measured by a radioenzymatic assay (Peuler & In the four patients where the dose of tienilic acid Johnson, 1977). was also started at 250 mg but doubled every week (group C), PRA was increased after 1 week and Statistical analysis increased further with doubling doses of the drug. The PRA was significantly (P< 0.01) related The statistical methods used were Student's two (r= 0.94) to the daily dose of tienilic acid (expressed tailed t-test for paired data and regression analysis. in mg): log PRA = -0. 15 12 + 0.0013 daily dose. The dispersion of the data is given by standard error of the mean (s.e.mean). Except for ACE activity the 2. Time course of PRA changes during chronic treat- biochemical parameters were transformed to their ment with diuretics logarithms since only their log distribution was Gaus- sian. From the 3rd to the 48st week the patients were treated with a constant dose of either 100 mg hydrochlorothiazide (n = 5) or 250 mg tienilic acid Results (n = 5) or 1000 mg tienilic acid (n = 4). Compared to the run-in period PRA was significantly (P< 0.01) The general characteristics of the patients are given increased and no decline in PRA was seen during in Table 1. Their 24-h urinary sodium excretion prolonged diuretic treatment for up to 48 weeks. averaged 99.5 ± 14.1 mEq during placebo and did However switching the patients back to placebo (run- not change (P> 0.10) during treatment with diure- out period), provoked a decrease (P< 0.001) in tics. PRA after 1 month, at that time the PRA level was DIURETICS IN ESSENTIAL HYPERTENSION 389

'Tienilic acid 250 mg dal nounced during treatment with 1000 mg tienilic acid (P<0.001). Constant dose 20 b. Angiotensin I and IIA 2- to 3-fold increase in PA I and PA II was observed during chronic treatment /,//,/p~-= ------4 with hydrochlorothiazide or tienilic acid (Table 2). However the plasma ACE activity did not change =5 // (n n = 5) during chronic administration of diuretics. c. Aldosterone Plasma aldosterone concentration was 03 (n=5) increased (P< 0.05) during treatment with both (n = 5)(n=4 100 mg hydrochlorothiazide and 1000 mg tienilic acid, while the changes in PAC during treatment with 250 mg tienilic acid were not significant. At the out- w n 4 (~~~~~~~~~ patients visit, 3 months after the start of active diure- 10 tic treatment this increase in PAC was not accom- panied by any change in urinary sodium or potassium (n = , 3) excretion, or in serum sodium concentration. How- a-cL 5 (n= 3) 1|, ever the serum potassium concentration decreased _- significantly during chronic treatment with hydro- )r chlorothiazide or tienilic acid. 100 mg hydrochlorothiazide and 250 mg tienilic acid provoked ,' Weekly doubling dose a small decrease in serum potassium concentration respectively from 4.12 ± 0.15 to 3.44 ± 0.22 mEq/l 1.0 (P< 0.05) and from 4.07 ± 0.12 to 3.68 0.14 mEq/l (P< 0.05); while the decrease was significantly high-

_ er on 1000mg tienilic acid (from 4.08±0.12 to 0 5 3.23 ± 0.16 mEq/l; P< 0.01). (n -4) 4. Correlations between changes in PA II and PRA or PAC during 3 months treatment with diuretics 1000 mg 500 mg, The changes in PA II during treatment with 100 mg 250 mg Tienilic acid- 0.1 hydrochlorothiazide and 250 or 1000 mg tienilic acid

1 2 3 were significantly (P< 0.01) related (r= 0.74) to the corresponding changes in PRA (n = 14; log/A PA II = Times (weeks) 0.883 + 0.618 logAPRA). Also the increase in PAC was significantly (P< 0.01) related (r= 0.68) to the Figure 1 Changes (mea ± s.e.mean) in plasma renin activity (PRA) during the first 3 weeks of treatment with rise in PA II during treatment with 100 mg hydroch- either a fixed dose of tienilic acid (upper panel) or a lorothiazide and 1000mg tienilic acid (n= 9; weekly doubling dose of tenilic acid (lower panel). logAPAC = -0.909+0.602 logAPA II). However *P< 0.05, **P< 0.01 compared with the run-in period. during treatment with 250 mg tienilic acid PAC was not significantly increased and the changes in PAC not significantly different from the PRA level in the were also not related to the changes in PA II. run-in period.

3. Effect of 3 months diuretic treatment on plasma electrolytes and on the different components of the Discussion renin-angiotensin-aldosterone system 1. Plasma renin activity (PRA) a. Active, inactive and total renin Compared to the run-in period on placebo both (in) active and total Increased PRA was unanimously found during renin were significantly increased during treatment chronic treatment with hydrochlorothiazide (Max- with 100 mg hydrochlorothiazide, 250 mg or well & Gross, 1979; Huang et al., 1979; Bourgoignie 1000mg tienilic acid for 3 months (Table 2). The et al., 1968; Sambhi, Eggena et al., 1976), with increases with 100 mg hydrochlorothiazide and tienilic acid (Maxwell & Gross, 1979; Huang et al., 250 mg tienilic acid were similar but were more pro- 1979) or with metolazone (Dornfeld & Kane, 1977) 390 P. LIJNEN, R. FAGARD, J. STAESSEN & A. AMERY

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Figure 2 Changes (mean±s.e.mean) in plasma renin activity (PRA) during chronic diuretic treatment. **P< 0.002, ***P< 0.001 compared with placebo. while the degree of stimulation of PRA and the time rather constant level, probably somewhat lower than of course of PRA changes differs from study to study. the maximum level reached after 1 week. The mag- In the present study using a constant but rather small nitude of the latter PRA increase during chronic daily dose of tienilic acid (250 mg) we found a maxi- treatment is dose dependent, ranging from a 2-fold to mal increase in PRA after one week and a levelling- a ten-fold (Table 2) increase above the pre-treatment off during the second and third week (Figure 1). level. However if the dose of tienilic acid was weekly doubled, a further rise in PRA was obtained (Figure 2. Plasma angiotensin II 1). The increase of PRA was thus dose-dependent. Treatment with hydrochlorothiazide and tienilic The chronic stimulation of PRA during long-term acid for 3 weeks caused a significant rise in PRA use of hydrochlorothiazide or tienilic acid in the (Figure 2) and no substantial decline during pro- treatment of essential hypertension was accom- longed treatment for 48 weeks was observed. How- panied by a significant rise in endogenous angioten- ever chronic hydrochlorothiazide therapy has been sin I and angiotensin II concentrations while the reported to increase renin less than acute administra- angiotensin converting enzyme activity was not tion (Bourgoignie et al., 1968). Similarly a compara- changed (Table 2). These results are in contrast with tive study of Sambhi, Eggena et al. (1976) shows that the early findings of Catt etaaL (1970) who found that the increase in PRA after 14 weeks of metolazone or during chronic diuretic administration, blood an- hydrochlorothiazide treatment was less than after 1 giotensin II was not elevated in patients with essential week of diuretic treatment. According to Maxwell & hypertension. Sambhi, Barrett et al. (1976) found a Gross (1979) chronic hydrochlorothiazide treatment significant, positive correlation (r-value between provoked a three-fold increase in PRA after 1 week 0.33 and 0.61) between blood angiotensin II and and subsequently a decrease to a level which was still PRA during treatment with 100mg hydroch- 1.7 times higher than the pre-treatment level; while lorothiazide of 5 mg metolazone for 1, 4 and 9 weeks. chronic tienilic acid therapy increased PRA after 1 Beyond 14 weeks of treatment this correlation was week and did not change further. absent (r= 0. 16). In the latter study blood angioten- In summary, literature data and our data suggest sin levels return to control levels despite sustained that on constant diuretic therapy PRA increases elevations of PRA. This progressive dissociation be- acutely and reaches a maximum within the first week, tween PRA and PA II suggests according to Sambhi, decreases during the next two weeks (Figure 1) but Barrett et al. (1976) that long-term adaptive remains elevated. During chronic diuretic therapy changes, including induction of enzymes and/or their from 1 month to 1 year, PRA remain elevated at a modification by inhibitors of activators has occurred, 392 P. LIJNEN, R. FAGARD, J. STAESSEN & A. AMERY thus altering the generation rate or metabolic clear- can at least be partly attributed to the dose of the used ance of angiotensin. In the present study we found drugs. Indeed we also found only a significant in- however a significant positive correlation between crease in plasma aldosterone during treatment with changes in PRA and PA II provoked by treatment 1000 tienilic acid for 3 months but not with 250 mg with hydrochlorothiazide or tienilic acid even after 3 tienilic acid. months. The authors gratefully acknowledge the technical and sec- 3. Plasma aldosterone retarial assistance of Miss L. Lommelen, Mrs S. Thielemans-Taelemans, Mrs K. Vanhoorenbeeck- dur- Bijttebier, Mrs M. Cober-Stinissen, Mr L. Cock and Mr J. The significant increases in plasma aldosterone Huysecom. ing chronic treatment with 100 mg hydroch- Limited to the We thank Smith, Kline and French Laboratories lorothiazide or 1000 mg tienilic acid is related for the generous supply of tienilic acid. rise in PA II. The work of this laboratory is supported in part by the In the study of Maxwell & Gross (1979) plasma Belgian I.W.O.N.L. aldosterone was not significantly changed during Reprint requests should be addressed to Dr P. Lijnen, long-term therapy with 50mg hydrochlorothiazide Hypertension Unit, Campus Gasthuisberg, Herestraat 49, or 250 mg tienilic acid. These controversial results B-3000 Leuven, Belgium.

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