Nitrate Tolerance Impairs Nitric Oxide-Mediated Vasodilation in Vivo

Cardiovascular Research ELSEVIER Cardiovascular Research 3 1 ( 1996) 8 14-8 19

Nitrate tolerance impairs nitric oxide-mediated vasodilation in vivo Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 Jgrn Beth Laursen * , Ssren Boesgaard, Henrik Enghusen Poulsen, Jan Aldershvile

Received 30 March 1995; accepted 1I December 1995

Abstract

Objectives: Nitroglycerin (NTG) is metabolized to nitric oxide (NO) m vascular smooth muscle cells. It is currently not clear whether prolonged exposure to NTG and tolerance development directly affects endogenous NO-mediated vasodilation in vivo. This study investigates NO-mediated vasodilation in conscious chronically catheterized rats before and after development of nitrate tolerance. The effect of the thiol compound N-acetylcysteine (NAC), which may affect NTG responsiveness, was also studied. Methods: Nitrate tolerance was induced by a 72-h intravenous infusion of NTG and confirmed by a 65-68% reduction in the hypotensive response to NTG (P < 0.05). The hypotensive effects of acetylcholine (ACh) and sodium nitroprusside, (SNP) and possible NAC-mediated changes in the responses to these compounds were examined in nontolerant and nitrate-tolerant rats. Furthermore, the hypertensive response to the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) was measured. Results: Nitrate tolerance was associated with a significantly attenuated hypotensive response to ACh (before 24 f. 1 mmHg; after 17 + 2 mmHg, n = 7, P < 0.05). Similarly, the response to SNP was reduced from 32 L- 1 mmHg to 26 f 3 mmHg (n = 7, P < 0.05). NTG-vehicle (placebo) did not affect the response to ACh and SNP (P > 0.05). NAC augmented the effect of NTG, ACh and SNP in both nontolerant and nitrate-tolerant animals (P < 0.05). The hypertensive response to L-NAME (n = 8) was reduced by 67% (from 34 + 6 mmHg to 1 I + I mmHg, P < 0.05) after induction of nitrate tolerance. Conclusions: The results suggest (1) that nitrate tolerance in vivo is associated with cross tolerance to NO-mediated vasodilation produced by both exogenous and endogenous nitrovasodilators and (2) that also responses to nitrovasodilator agents other than NTG are improved by the addition of NAC.

Keyword.ct Nitrates; Nitrate tolerance; Nitric oxide; Acetylcholine; N-acetylcysteine; L-NAME; Rat, anesthetized

1. Introduction Recent in vitro data suggest that nitrate tolerance may be associated with an impaired function of NO probably Nitric oxide (NO) is an important endogenousregulator caused by nitrate-mediated changesin the oxidative milieu of vascular tone and accounts for the clinical effects of [ 131. In addition, exogenously added NO causes a re- organic nitrates [ 1,2]. Continuous administration of organic versible inhibition of the synthesis of the endothelium-de- nitrates (e.g. nitroglycerin (NTG) and isosorbide-dinitrate rived NO in vitro [I 41. Thus, it is possible that prolonged (ISDN)) leads, however, to tolerance of their hemody- nitrate therapy directly affects endogenous NO-mediated namic and clinical effects [3-51. The phenomenon of vasodilation. However, despite important clinical implica- nitrate tolerance is complex and still not understood. Some tions, the in vivo effect of nitrates on the endogenous of the mechanismsunderlying tolerance development may vascular NO pathway is currently not clear. include reduced bioconversion of the vasoinactive parent The purpose of this study was to determine whether compound to NO [2,6,7] and neurohormonal activation, nitrate tolerance affects the endogenous NO pathway in counteracting nitrate-induced NO-mediated vasodilation vivo. Endothelium-dependent and endothelium-indepen- [g-lo]. However, other mechanismsmay also play a role dent NO-mediated vasodilation was measuredbefore and 111,121. after development of nitrate tolerance. Thiol compounds have previously been shown to modify nitrate responsive-

’ Corresponding author. Medical Department B 2142, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. Fax: ( + 45-3 I) 38 3 1 86. Time for primary review 33 days.

ness [15-211, thus, the influence of the thiol compound 2.3. Experimental protocol N-acetylcysteine (NAC) on NO-mediated vasodilation was also investigated. Six different groups of conscious chronically catheterized rats were studied. In the 3 groups receiving prolonged NTG infusion, nitrate tolerance was confirmed by the response to NTG bolus infusions as described above. 2. Materials and methods 2.3.1. NO-mediated vasodilation in nontolerant and ni- 2.1. Animals Irate-tolerant rats Two groups of rats were investigated. Seven rats re- Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 ceived longterm infusion of NTG (0.2 mg/h) for 3 days Specific-pathogen-free female Wistar rats (200 to 250 (NTG-tolerant group). Another seven rats received NTG- g) were housed under constant temperature and humidity vehicle infusion for a similar period of time (NTG-placebo). conditions. Light was controlled in a 12/12 h light-dark In each group a NO-mediated reduction in mean arterial cycle. Before and during the experimental period, all rats blood pressure (MAP) was induced before and after 3 days had free access to a standard rat chow and tap water. The (72 h) of NTG/placebo infusion. Endothelium-dependent rats were anesthesized with 1 to 3% halothane and N,O/O, NO-mediated vasodilation was examined using acetyl- (2:l). One catheter (medical-grade Tygon catheters) was choline (ACh) and endothelium-independent NO-mediated implanted with the tip in the ascending aorta through the vasodilation using sodium nitroprusside (SNP). Both ACh left carotid artery, and 3 separate catheters were placed in (10 pg/kg) and SNP (20 pg/kg) were administered as a the superior vena cava via the left (2) and right (1) jugular bolus i.v. infusion (0.4 ml over 60 s) separated by a 20 min vein. Catheters were filled with a solution of 50% glucose interval allowing MAP to recover to the baseline value. and 500 IU heparin/ml and plugged with a nylon pin. Based on previous dose-response experiments, submaximal Each catheter was externalized through the back in the (in the range of ED,,-ED,,) doses of ACh and SNP were neck region and secured by a polyester felt disc placed in chosen and expected to elicit a fall in MAP of approxi- the subcutis. After implantation of catheters, the rats were mately 30 mmHg in normal untreated rats. Isotonic saline housed individually until they had regained their preopera- was used as control. tive weight and appeared healthy (6 to 8 days after catheter implantation). All experiments were performed in conscious unrestrained rats. 2.3.2. Thiol supplementation and NO-mediated uasodilation in nontolerant and nitrate-tolerant rats On day 3, after completion of the experiments described 2.2. Induction of nitrate tolerance above, the same two groups of rats received NAC (5 mmol/kg per h intravenously (1.5 ml/h) for 3 h) in addition to the ongoing NTG/placebo infusion. The hemo- At the end of the recovery period (day 0), the hemody- dynamic responses to ACh, SNP and NTG were repeated namic response to NTG was determined from the blood during the last infusion hour. pressure lowering effect of intravenous bolus infusions (0.4 ml over 60 s) of NTG (0 mg (placebo) and 5 mg NTG) separated by a 20 min interval. An osmotic 2.3.3. Nitrate tolerance and NO synthase inhibition minipump (Alza Corp.) was then placed subcutaneously The hemodynamic effect of endothelial NO synthase and connected to one of the 3 i.v. catheters. NTG or inhibition by No-nitro-L-arginine-methyl ester (L-NAME) placebo (98% ethanol (NTG-vehicle)) was delivered from was studied in 2 other groups of rats (n = 8 in each the minipump at a constant rate of 0.2 mg/h i.v. (10 group). One group of normal nontolerant rats (control) and PI/h) throughout the study period. To confirm develop- one group of nitrate-tolerant rats (NTG-tolerant + L- ment of nitrate tolerance, the blood pressure lowering NAME) received intravenous I~-NAME (1.5 mg/kg) for effect of NTG/placebo bolus infusions was reexamined at 60 s. From dose-response experiments 1.5 mg L-NAME day 3 in all treatment groups. Baseline blood pressure per kg was expected to increase MAP by approximately 30 (before NTG/placebo bolus infusion) and blood pressure mmHg in normal nontolerant rats. changes during NTG/placebo bolus infusions were recorded continuously by pressure transducers (Baxter 2.3.4. NO-independent uasodilation in nontolerant and Corp, Uden, Netherlands) connected to the arterial catheter. nitrate-tolerant rats Tracings were displayed on a Graphtec linear recorder In order to investigate the effect of nitrate tolerance on (Watanabe Instruments Corp., Japan). The investigation NO-independent vasodilation, the effect of the calcium conforms with the Guide for the care and use of laborarory channel antagonist nimodipine (200 pg/kg, 0.4 ml over 1 animals published by the US National Institutes of Health min) was investigated before and after development of (NIH publication no. 85-23, revised 1985). nitrate tolerance in one additional group of rats receiving 816 J.B. Luursrn et ul./Curdio~u~culur Rueurch 31 (1996) 814-819

NTG for 72 h (II = 6) and a comparable control group NTG-placebo NTG tolerant receiving NTG vehicle (n = 4). groupgroup 2.4. Drugs

NTG solutions were prepared from a stock solution (100 mg NTG in 1 ml of 98% ethanol). For prolonged infusion, NTG was further diluted in 98% ethanol (20 mg/ml). All other solutions were prepared in 0.9% saline and adjusted to pH 7.4. Ach, SNP, L-NAME were pur- rr Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 chased from Sigma Chemical Co, St. Louis, MO. NAC (MucomystR) was kindly delivered by ASTRA A/S, Copenhagen,Denmark. I ~‘0.06 2.5. Calculations and statistics

Mean arterial blood pressure (MAP) was estimated as diastolic pressureplus (systolic minus diastolic pressure)/3 in mmHg. The reported changesin MAP to ACh and SNP represent the difference between the baseline MAP (im- mediately before ACh and SNP) and the nadir on the blood pressurecurve after ACh and SNP. The hypertensive ~‘0.06 effect of L-NAME was calculated as the maximum in- -80’ crease from baselineMAP after i.v. L-NAME administra- 0~0.06 tion. All data are presented as mean + s.e.m. In the 2 groups receiving NAC, differences within each group were determined by a repeated measuresanalysis of variance. In the other experiments differences within groups (pre- and posttreatment means>were determined by Student’s paired t-test. Within each set of experiments comparisons between the study group and the control group were done ~‘0.06 with Student’s t-test for unpaired samples.Statistical sig- nificance was assumedwhen P < 0.05. -60 J ~‘0.06

3. Results

Oh 72h NAC Oh 72h NAC 3.1. Induction of nitrate tolerance Fig. I Bar graps showing the hypotensive effects of NTG, ACh and SNP in two groups of rats (n = 8 in each group) before (0 h) and after a 72 h In the 3 groups of rats infused with NTG for 3 days, (72 h) intravenous infusion of either NTG vehicle (NTG-placebo, left development of nitrate tolerance was confirmed by a 68%, panel) or NTG 0.2 mg/h (NTG-tolerant, right panel). In each group the 67% and 65% reduction (compared with preinfusion) in effect of additional thiol supplementation with NAC (5 mmol/kg per h for 3 h) is also shown (NAC). P < 0.05: significantly different from 72 h. the hypotensive effect of bolus NTG (NTG-tolerant group: from 25 + 3 mmHg to 8 + 1 mmHg (Fig. 1); NTG- tolerant/L-NAME group: from 34 k 6 to 11 k 1 mmHg; caused no significant changes in MAP in any of the NTG-tolerant/nimodipine group: from 26 f 2 to 9 + 1 experiments (data not shown). mmHg, P < 0.05). The response to NTG in the groups infused with NTG-vehicle did not change during the 3-day 3.2. NO-mediated uasodilation in nontolerant and nitrate- infusion period (P > 0.05) (Fig. 1). Baseline MAP values tolerant rats (before NTG bolus challenges) were similar in all treatment groups and did not change (P > 0.05) during the The hypotensive effect of ACh was reduced by 29% experimental period (0 h vs 72 h, NTG-tolerant group: after development of nitrate tolerance (NTG group); (from 110 -t 2 vs 107 + 5 mmHg; NTG-tolerant/L-NAME 24 f 1 mmHg at day 0 (before NTG infusion) to 17 f 2 group: 106 * 4 vs 109 * 6; NTG-tolerant/nimodipine mmHg at day 3 after 72 h of NTG infusion) (Fig. 1). group: 111 k 5 vs 108 f 3 mmHg; NTG-placebo: 106 + 4 Similarly, the fall in MAP induced by SNP was reduced by vs 108 + 5 mmHg1. Bolus dosesof saline and NTG-placebo 19% from 32 -t 1 mmHg to 26 f 3 mmHg (P < 0.05) J.B. Lowsen er ul./Curdiouuscular Rrseurch 31 (1996) 814-819 817

after development of nitrate tolerance (Fig. 1). The data sodilation by nimodipine was not affected by the develop- suggest that development of nitrate tolerance in vivo is ment of nitrate tolerance. Nimodipine reduced MAP by associated with a significant attenuation of both endothe- 26 & 4 mmHg before the NTG infusion and by 25 k 3 lium-dependent (ACh) and endothelium-independent (SNP) mmHg after the development of nitrate tolerance (P < NO-mediated vasodilation. The effect of nitrate tolerance 0.05). In the corresponding control animals the responses on the responses to ACh and SNP is, however, less were 25 + 2 and 24 + 2 mmHg respectively. pronounced than the effect on NTG responsiveness (P < 0.05) (NTG group). Infusion of NTG-vehicle (placebo group) did not affect responses to ACh and SNP (Fig. 1). 4. Discussion Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 3.3. Thiol supplementation and NO-mediated vasodilation A major finding of this in vivo study is that develop- in nontolerant and nitrate-tolerant rats ment of nitrate tolerance is associated with significant impairments of the vascular effects of endothelium-depen- NAC administration significantly potentiated the effect dent NO agonist (ACh) and antagonist (L-NAME) treat- of all the 3 drugs used to induce NO-mediated vasodilation ment. Thus, prolonged adminstration of an exogenous (i.e. NTG, ACh and SNP) in both nitrate-nontolerant and nitrovasodilator and development of in vivo nitrate toler- nitrate-tolerant rats (Fig. 1). Intriguingly, the responses to ance significantly interferes with the endogenous nitrova- NTG, ACh and SNP in nitrate-tolerant rats treated with sodilator pathway for vascular relaxation. NAC were not different from either the initial NTG re- Vascular (endothelial) NO is produced from L-arginine sponses before longterm infusion of NTG or the responses [22]. The process is controlled by the enzyme, NO-syn- seen after 72 h in the NTG-placebo group (Fig. 1). thase, which can be stimulated by both receptor-dependent agonists (e.g. ACh) and physical stimuli or inhibited by 3.4. Nitrate tolerance and NO synthase inhibition L-arginine analogs (e.g. L-NAME) [23]. NO activates solu- ble guanylate cyclase and the subsequent increase in cyclic An effect of nitrate tolerance development on endothe- GMP leads to smooth muscle relaxation [24]. Organic lial NO regulation is further substantiated by the observa- nitrates and SNP are converted directly to NO and “by- tion of a marked reduction (62%) in the blood pressure pass” the endogenous NO synthesis. However, they paral- response to NO synthase inhibition with L-NAME (Fig. 2). lel the biological actions of endogenous NO due to the In the group of normal nontolerant rats (L-NAME group) common final pathway (i.e. activation of guanylate cy- MAP increased by 29 f 6 mmHg whereas MAP increased clase). only 11 f 1 mmHg in nitrate-tolerant animals (NTG- In the present study marked tolerance to the hemody- tolerant/L-NAME group) (P < 0.05). namic effects of NTG developed after intravenous infusion of NTG in conscious rats. However, not only the response 3.5. NO-independent vasodilation in nontolerant and ni- to NTG, but also the responses to ACh, L-NAME and SNP trate-tolerant ruts were significantly attenuated, suggesting the existence of a certain degree of cross tolerance between NTG and other In contrast to the drugs inducing NO-mediated vasodila- compounds modulating NO-mediated vasorelaxation. In- tion, NO-independent (and endothelium-independent) va- terestingly, NO-independent vasodilation, as measured by the response to nimodipine, was not affected by tolerance 40 development, suggesting that the observed cross tolerance 7i 1 is specific for nitrovasodilator substances. Data from previous in vitro studies have been conflict- ing 125-351. In general, experiments performed strictly in vitro, incubating vessels with high concentrations of NTG [25-291, have not been able to show the existence of cross tolerance to other nitrovasodilators whereas more physio- P'O.05 logical approaches using in vivo NTG exposure and subsequent in vitro testing [ 11,13,32] are more compatible with the present strictly in vivo setup. Thus, the present finding is compatible with recent reports [ 13,341 stressing the differences between results obtained by in vitro methods of

non-tolerant nitrate tolerant tolerance development as compared with methods of in vivo nitrate tolerance development. Fig. 2. Bar graph showing the increase in mean arterial blood pressure Mechanisms responsible for a nitrate-induced develop- (MAP) after infusion of the NO synthase inhibitor L-NAME (I .5 mg/kg) in normal nontolerant rats (n = 8) and nitrate-tolerant rats (n = 8). P < ment of cross tolerance between NTG and other NO 0.05: significantly different from control. releasing substances may include either a downregulation 818 J.B. Laursrn et al./Curdiovasculur Resrurch 31 (19961 814-819 of endogenous endothelial NO synthesis and/or an im- the microcirculation [41,43,44]. As suggestedby the lack paired effect of NO itself (e.g. desensitization of guanylate of tolerance specificity and the present finding of a thiol- cyclase). In vitro, administration of different NO-donor induced change in the in vivo effect of other NO donors as agents including NTG may inhibit endothelial NO syn- well, the effect of thiols may be rather nonspecific. Since thase [14]. It is tempting to speculate that a NO-induced antioxidants like superoxide dismutase [13] and ascorbic (NTG) negative feed-back regulation on endothelial NO acid [45] may also increasethe vascular effects of SNP and synthaseand thus decreasedendogenous vasodilator forces ACh, it is possible that an effect of thiol supplementation may contribute partly to the hemodynamic signs of nitrate may at least partly be related to its vascular reducing tolerance. However, while our findings of decreasedre- capacity. In this context it is interesting that NAC has been

sponses to ACh and L-NAME are compatible with a shown to prolong the half live of endothelium-derived Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 nitrate-induced inhibition of endothelial NO synthase,such relaxing factor in vitro [46,47]. a mechanismdoes not explain the reduced effect of NTG In summary, this study showsthat hemodynamic toler- and SNP in this and other studies [ 11,13,30-33,351. It is ance to NTG is accompanied by an in vivo attenuation of therefore of note that Miinzel and coworkers [13] recently both endothelium-dependent (ACH, L-NAME) and en- reported that NTG treatment is associated with an in- dothelium-independent NO-mediated effects (SNP). It is creased endothelial production of reactive oxygen species concluded that (1) nitrate tolerance in vivo is associated in nitrate-tolerant aorta segments.These changesmay af- with cross tolerance to NO-mediated vasodilation pro- fect the efficacy of NO per se [36]. The fact that the duced by both exogenous and endogenous nitrovasodila- antioxidant, superoxide dismutase (scavenging 0;) tors and (2) reduced effects of NO-dependent vasodilators markedly enhancedrelaxations to NTG, SNP and ACh (all may contribute to the development of nitrate tolerance in releasing NO by different mechanisms)[ 131 further sug- vivo. geststhat increasedoxidative stressand increaseddegrada- tion of NO by reactive oxygen speciesmay contribute to the development of both nitrate tolerance and cross toler- Acknowledgements ance. This hypothesis may account for (1) the observed reduction in endothelium-dependentNO-mediated vasore- This study was supported by grants from the Danish activity (ACh and L-NAME), (2) the reduced hypotensive Heart Foundation and The J@rgenMerller Foundation. effect of SNP and (3) the potentiated hypotensive effect of NTG, SNP and ACh after administration of NAC which has both extracellular and intracellular antioxidant properties. References The reduced responseto L-NAME in tolerant rats sug- gests that nitrate tolerance inhibits endogenous NO-syn- [II Ignarro LJ, Lippton H, Edwards JC, Baricos WH, Hyman AL, Kadowitz PJ, Gruetter CA. Mechanisms of vascular smooth muscle thase activity and/or that basicly produced NO is rapidly relaxation by organic nitrates, nitrites, nitroprusside and nitric oxide. inactivated. In as much as the responseto L-NAME may Evidence for the involvement of S-nitrosothiols as active intermedi- be considered as a marker of the contribution of basicly ates. J Pharmacol Exp Ther I98 I ;218:739-749. produced NO to the regulation of vascular tone, the present [21 Chung SJ, Fung HL. Relationship between nitroglycerin-induced results are compatible with the assumption that nitrate vascular relaxation and nitric oxide production. Biochem Pharmacol tolerance not only has a detrimental effect on agonist-in- 1993;45:157-163, [31Thadani U, Fung HL, Da&e AC, Parker JO. Oral isosorbide dini- duced NO-mediated vasodilation but also affects the basal trate in angina pectoris: comparison of duration of action and regulation of vascular tone. dose-response relation during acute and sustained therapy. Am J Tolerance to NTG was significantly more pronounced Cardiol 1982;49:41 l-41 9. than tolerance to ACh and SNP. This observation stresses [41Zimrin D, Reichek N. Bogin KT, Aurigemma G, Douglas P, Berko that other (nitrate specific) mechanisms (e.g. impaired B, Fung HL. Antianginal effects of intravenous nitroglycerin over 24 hours. Circulation 1988;77: 1376- 1384. bioconcersion of NTG) also may contribute to in vivo [51 Boesgaard S, Aldershvile J, Paulsen HE. Preventive administration tolerance development to organic nitrates. of intravenous N-acetylcysteine and development of tolerance to Coadministration of thiols and NTG have previously isosorbide dinitrate in patients with angina pectoris. Circulation been shown to augment the in vivo circulatory responseto 3992;85:143-149. id Slack CJ, McLaughlin BE, Nakatsu K, Marks GS, Brie, JF. Nitric NTG both in nontolerant [34,37,38] and nitrate-tolerant oxide-induced vasodilation of organic nitrate-tolerant rabbit aorta. conditions [5,19,21]. Data on in vitro NTG/thiol interac- Can J Physiol Pharmacol 1988;66: I34& 1346. tions are, however, more divergent [ 1.5- 17,39-411. The [71 Fiirster S, Woditsch I, Schriider H, Schrar K. Reduced nitric oxide mechanismsunderlying such an interaction are not clear, release causes nitrate tolerance in the intact coronary circulation. J but in addition to the specific cofactor requirement of thiol Cardiovasc Pharmacol I99 I ; I7:867-872. Packer M, Lee WH, Kessler PD, Gottlieb SS, Medina N, Yushak M. compounds for the conversion of organic nitrates to NO [81 Prevention and reversal of nitrate tolerance in patients with conges- [1,34,42], thiols like NAC may induce the formation of tive heart failure. N Engl J Med 1987;317:799-804. vasoactive nitrosothiols and improve the action of NTG on [91Parker JD, Farrell B, Fenton T, Cohanim M, Parker JO. Counter- J.B. Loursen rt al./ Cardiouusculrr Research 31 (1996) 814-819 819

regulatory responses to continuous and intermittent therapy with [31] Rapoport RM, Waldman SA, Ginsburg R, Molina CR, Murad F. nitroglycerin. Circulation I99 I ;84:2336-2345. Effects of glyceryl trinitrate on endothelium-dependent and -inde- [lo] Miinzel T, Sayegh H, Harrison DG. Nitroglycerin tolerance is pendent relaxation and cyclic GMP levels in rat aorta and human associated with increases in vascular constriction mediated by pro- coronary artery. J Cardiovasc Pharmacol 1987; 10:82-89. tein kinase C. Circulation 1994;9O(abstr): 1720. [32] Molina CR, Andresen JW, Rapoport RM, Waldman S, Murad F. [I I] Axelsson KL, Andersson RGG. Tolerance towards nitroglycerin, Effect of in vivo nitroglycerin therapy on endothelium-dependent induced in viva, is correlated to a reduced cGMP response and and independent vascular relaxation and cyclic guanosine alterations in cGMP turnover. Em J Pharmacol 1983;88:7 I-79. monophosphate accumulation in rat aorta. J Cardiovasc Pharmacol [I21 Waldmann SA, Rapoport RM, Ginsburg R, Murad F. Desensitiza- 1987;10:371-378. tion to nitroglycerin in vascular smooth muscle from rat and human. [33] Schriider H, Leitman DC, Bennett BM, Waldnamn SA, Murad F. Biochem Pharmacol 1986;35:3525-3531. Glyceryl trinitrate-induced desenitization of guanylate cyclase cy-

[13] Miinzel T, Sayegh H, Freeman BA, Tarpey M, Harrison DG. clase in cultured rat lung tibroblasts. J Pharmacol Exp Ther Downloaded from https://academic.oup.com/cardiovascres/article/31/5/814/317266 by guest on 29 September 2021 Evidence for enhanced vascular superoxide anion production in 1988;245:413-418. nitrate tolerance. J Clin Invest 1995;95: 187- 194. [34] Boesgaard S, Poulsen HE, Aldershvile J, Loft S, Anderson ME, [14] Buga GM, Griscavage JM, Rogers NE, lgnarro LJ. Negative feed- Meister A. Acute effects of nitroglycerin depend on both plasma and back regulation of endothelial cell function by nitric oxide. Circ Res intracellular sulfhydryl compound levels in vivo. Effect of agents 1993;73:808-812. with different sulthydryl modulating properties. Circulation [15] Torresi JT, Horowitz JD, Dusting GJ. Prevention and reversal of 1993;87:547-553. tolerance to nitroglycerine with N-acetylcysteine. J Cardiovasc Phar- [35] Fukazawa M. Namiki A. Reduced endothelium-dependent vasodila- macol 1985;7:777-783. tion by acetylcholine and bradykinin in isolated nitroglycerin-tolerant [16] Needleman P, Jakschik B, Johnson EM. Sulfhydryl requirement for blood vessels. Gen Pharmac 1994;25:61-67. relaxation of vascular smooth muscle. J Pharmacol Exp Ther [36] Gryglewski RJ, Palmer RM, Moncada S. Superoxide anion is in- 1973:187:32&331. volved in the breakdown of endothelium-derived vascular relaxing [ 171 Feelisch M, Noack EA. Correlation between nitric oxide formation factor. Nature (Land) 1986;320:454-456. during degradation of organic nitrates and activation of guanylate [37] Horowitz JD, Antman EM, Lorell BH, Barry WH, Smith TW. cyclase. Eur J Pharmacol 1987; 139: 19-30. Potentiation of the cardiovascular effects of nitroglycerin by N- [18] Chong S, Fung HL. Biochemical and pharmacological interactions acetylcysteine. Circulation 1983;68: 1247-1253. between nitroglycerin and thiols. Biochem Pharmacol [38] Fung HL, Chong S, Kowaluk E, Hough K, Kakemi M. Mechanisms 1991;42: 1433- 1439. for the pharmacologic interaction of organic nitrates with thiols. [I91 May DC, Popma JJ, Black WH, Schaeffer S. Lee HR, Levine BD, Existence of an extracellular pathway for the reversal of nitrate Hillis LD. In vivo induction and reversal of nitroglycerin tolerance vascular tolerance by N-acetylcysteine. J Pharmacol Exp Ther in human coronary arteries. N Engl J Med 1987;317:805-809. 1988;245:52&530. [20] Boesgaard S, Iversen H, Wroblewski H, Paulsen HE, Frandsen H, [39] Gruetter CA, Lemke SM. Dissociation of cysteine and glutathione Kastrup J, Aldershvile J. Altered peripheral vasodilatory profile of levels from nitroglycerin-induced relaxation. Eur J Pharmacol nitroglycerin during long-term infusion of N-acetylcysteine. J Am 1985;l I1:85-95. Co11 Cardiol 199423: 163- 169. [40] Henry PJ, Horowitz JD, Louis WJ. Determinants of in vitro nitro- [21] Boesgaard S, Aldershvile J, Poulsen HE, Loft S, Anderson ME, glycerin tolerance induction and reversal: influence of dose regimen, Meister A. Nitrate tolerance in vivo is not associated with depletion nitrate-free period, and sulfhydryl supplementation. J Cardiovasc of arterial or venous thiol levels. Circ Res 1994;74: 115- 120. Pharmacol 1989; 14:3l-37. [22] Palmer RMJ, Ashton D, Moncada S. Vascular endothelial cells [41] Sellke FW, Tomanek RJ, Harrison DG. L-cysteine selectively poten- synthesise nitric oxide from L-arginine. Nature 1988;333:664-666. tiates nitroglycerin-induced dilation of small coronary microvessels. [23] Moncada S, Higgs EA. Endogenous nitric oxide: physiology, pathol- J Pharm Exp Ther 1991;258:365-369. ogy and clinical relevance. Eur J Clin Pharmacol 1991;21:36 1-374. [42] Harrison DG, Bates JN. The nitrovasodilators: new ideas about old ]24] Rapoport RM, Murad F. Agonist-induced endothelium-dependent drugs. Circulation 1993;87:652-659. relaxation in rat thoracic aorta may be mediated through cyclic ]43] Myers PR, Minor RL, &terra R, Bates JN, Harrison DG. Vasorelax- guanosine monophosphate. Circ Res 1983;52:352-357. ant properties of the endothelium-derived relaxing factor more closely [25] Kowaluk EA, Poliszcuk R, Fung HL. Tolerance to relaxation in rat resemble S-nitrosocysteine than nitric oxide. Nature 1990;345: 161- aorta: comparison of an S-nitrosothiol with nitroglycerin. Eur J 163. Pharmacol 1987; 1441379-383. [44] Kurz MA, Lamping KG, Bates JN, Eastham CL, Marcus ML, [26] Voorde JV, Vanheel B, Leusen I. Influence of vascular tolerance to Harrison DG. Mechanisms responsible for the heterogeneous coro- nitroglycerin on endothelium-dependent relaxation. Arch Int Phar- nary microvascular response to nitroglycerin. Circ Res macodyn 1987;290:215-221. 1991;68:847-855. ]27] Milsch A, Busse R, Bassenge E. Desensitization of guanylate [4.5] Laursen JB, Boesgaard S, Paulsen HE, Aldershvile J. Vitamin C and cyclase in nitrate tolerance does not impair endothelium-dependent thiol supplementation potentiate receptor stimulated nitric oxide responses. Eur J Pharmacol 1988;158:191-198. release in viva. Circulation 1994,90(abstr): 1301. [28] Mtilsch A, Busse R, Winter I, Bassenge E. Endothelium- and [46] Stamler J, Mendelsohn ME, Amarante P, et al. N-acetylcysteine sydnonimine-induced responses of native and cultured aortic smooth potentiates platelet inhibition by endothelium-derived relaxing fac- muscle cells are not impaired by nitroglycerin tolerance. Naunyn- tor. Circ Res 1989;65:789-795. Schmiedebergs’s Arch Pharmacol 1989;339:568-574. ]47] Cooke JP, Stamler J, Andon N, Davies PF. McKinley G, Loscalzo J. [29] Lawson DL, Nichols WW, Mehta P, Metha JL. Captopri-induced Flow stimulates endothelial cells to release a nitrovasodilator that is reversal of nitroglycerin tolerance: role of sulfhydryl group vs potentiated by reduced thiol. Am J Physiol 1990;259:H80&H812. ACE-inhibitory activity. J Cardiovasc Pharmacol 1991; 17:411-418. [30] Kukovetz WR, Holzmann S. Mechanism of nitrate-induced vasodilation and tolerance. 2 Cardiol 1983;72(suppl 3): l4- 19.