S-nitrosating nitric oxide donors induce long-lasting inhibition of contraction in isolated arteries.

The ability of various nitric oxide (NO) donors to induce long-lasting inhibition of contraction in isolated arteries was compared. All the studied compounds elicited a relaxant effect in rat aortic rings precontracted with norepinephrine (NE). Almost maximal relaxation was obtained with 1 microM of each compound. The S-nitrosating agents S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine, S-nitroso-N-acetylcysteine, and sodium nitroprusside (1 microM) produced a decrease of the maximal effect of NE that persisted after removal of the drug. This hyporesponsiveness to NE was associated with a relaxant effect of N-acetylcysteine, a low-molecular weight thiol that can displace NO from cysteine-NO bonds. Such modifications of contraction were not observed in aortic rings previously exposed to 1 microM S-nitrosocysteine, glyceryl trinitrate, 3-morpholinosydnonimine, or 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA-NO). The same differential effects of GSNO and DEA-NO on contraction were also observed in porcine coronary arteries. Rat aortic rings previously exposed to 100 microM GSNO, but not to 100 microM DEA-NO, displayed a persistent increase in NO content (determined by NO spin trapping) and cysteine-NO residues (determined by immunostaining with an anti-cysteine-NO antiserum). The GSNO-induced increase in cysteine-NO residues in aortic tissue was prevented by the thiolmodifying agent p-hydroxymercuribenzoic acid. This study shows that in isolated arteries, the effects of S-nitrosating agents differed from those of other NO-donating agents. S- Nitrosating agents induced a persistent inhibition of contraction, which was attributed to the formation of releasable NO stores by S-nitrosation of tissue thiols. These differential effects of NO donors may be important for orientating their therapeutic indications.