AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 3 767-R772, Copyright © 1994 by American Physiological Society

ARTICLES

N-acetyl-L-cysteine potentiates depressor response to captopril and enalaprilat in SHRs

F. J. Ruiz, M. G. Salom, A. C. Ingles, T. Quesada, E. Vicente and L. F. Carbonell
Departamento de Fisiologia Humana, Facultad de Medicina, Murcia, Spain.

Recently, in vivo and in vitro studies have implicated nitric oxide as a mediator of the vascular effects of angiotensin-converting enzyme inhibitors (ACEIs). In the present study we hypothesized that N-acetyl-L-cysteine (NAC), by increasing the availability of reduced sulfhydryl groups, would enhance the antihypertensive response to the ACEIs captopril and enalaprilat by a mechanism dependent on nitric oxide. The experiments were performed on instrumented, indomethacin-pretreated, awake spontaneously hypertensive rats (SHRs). Thirty minutes after a bolus of captopril (10 mg/kg iv) was administered, blood pressure decreased from 167 +/- 5 to 147 +/- 6 mmHg (n = 8). The pretreatment with the donor of thiol groups NAC (300 mg/kg iv) potentiated the depressor response to captopril because blood pressure decreased from 172 +/- 3 to 139 +/- 4 mmHg (n = 6). At the dose of 60 micrograms/kg iv, the ACEI enalaprilat did not acutely modify the blood pressure of SHRs (from 172 +/- 5 to 167 +/- 4 mmHg; n = 6). However, when the SHRs were pretreated with NAC, the same dose of enalaprilat significantly reduced blood pressure from 176 +/- 5 to 151 +/- 5 mmHg (n = 6). This potentiation of the depressor response to ACEIs, due to NAC, was not observed when SHRs were pretreated with the nitric oxide inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 50 micrograms.kg-1.min-1 iv). The results of this study suggest that NAC, a donor of sulfhydryl groups, potentiates the antihypertensive response to captopril and enalaprilat in SHR by a nitric oxide-dependent mechanism.

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