Inhibitory effects of S-nitrosocaptopril on vasomotor tone.

AIM: To study effects of captopril (Cap) and S-nitrosocaptopril (CapNO) on vascular tension. METHODS: Tension of rabbit aortic rings and perfusion pressure of rat renal artery (PPr) were examined to evaluate the effects of CapNO. RESULTS: CapNO (3 nmol.L-1-10 mumol.L-1) produced concentration-dependent vasorelaxation response in the rings of rabbit thoracic aortas. Endothelium denudation did not alter the relaxations to CapNO. In contrast, Cap had no vasorelaxing effect on the rings precontracted with phenylephrine. CapNO (10 nmol.L-1) decreased rat PPr in vivo (P < 0.01), and the effect was concentration-dependent and reversible. Cap showed a reduction in rat PPr only at the concentration 1000 nmol.L-1 (P < 0.05). The relaxing potency of CapNO was 100 times higher than that of Cap in this respect. Pre-perfusion of rat renal arteries with NG-monomethyl-L-arginine monoacetate (L-NMMA, 0.03 nmol.L-1) or L-arginine (3 nmol.L-1) did not significantly blocked the relaxing effect induced by CapNO. CONCLUSION: CapNO had a direct vasodilatory effect.