In vivo evidence that L-S-nitrosocysteine may exert its vasodilator effects by interaction with thiol residues in the vasculature

This study examined the effects of the lipophobic thiol chelator, para-hydr oxymercurobenzoic acid (25 and 50 mu mol/kg, i.v.) on the falls in mean art erial blood pressure and regional vascular resistances produced by L-S-nitr osocysteine (400 nmol/kg, i.v.) and the nitric oxide (NO)-donors, (Z)-1-\N- methyl-N-[6(N-methylammoniohexyl)amino]\diazen-1-ium-1,2-diolate (MAHMA NON Oate, 25 nmol/kg, i.v.) and sodium nitroprusside (10 mu g/kg, i.v.), in ure thane-anesthetized rats. The L-S-nitrosocysteine-induced responses were mar kedly diminished whereas the MAHMA NONOate- and sodium nitroprusside-induce d responses were minimally affected by para-hydroxymercurobenzoic acid. The se results suggest that the vasodilator actions of L-S-nitrosocysteine invo lves the interaction with membrane thiols in vascular smooth muscle of resi stance arteries and that para-hydroxymercurobenzoic acid does not markedly affect NO-mediated vasodilation. (C) 1999 Elsevier Science B.V. All rights reserved.