PEROXYNITRITE-INDUCED ACCUMULATION OF CYCLIC-GMP IN ENDOTHELIAL-CELLSAND STIMULATION OF PURIFIED SOLUBLE GUANYLYL CYCLASE - DEPENDENCE ON GLUTATHIONE AND POSSIBLE ROLE OF S-NITROSATION

Peroxynitrite (ONOO-) is widely recognized as mediator of NO toxicity, but recent studies have indicated that this compound may also have ph ysiological activity and induce vascular relaxation as well as inhibit ion of platelet aggregation. We found that ONOO- induced a pronounced increase in endothelial cyclic GMP levels, and that this effect was si gnificantly attenuated by pretreatment of the cells with GSH depleting agents. In the presence of 2 mM GSH, ONOO- stimulated purified solubl e guanylyl cyclase with a half maximally effective concentration of ab out 20 mu M. In contrast to the NO donor 2,2-Diethyl-1-nitroso-oxyhydr azine sodium salt (DEA/NO), ONOO- was completely inactive in the absen ce of GSH, indicating that thiol-mediated bioactivation of ONOO- is in volved in enzyme stimulation. Studies on the reaction between ONOO- an d GSH revealed that about 1% of ONOO- was non-enzymatically converted to S-nitrosoglutathione. The authentic nitrosothiol was found to be st able in solution, but slowly decomposed in the presence of GSH. GSH-in duced decomposition of S-nitrosoglutathione was apparently catalyzed b y trace metals and was accompanied by a sustained release of NO and a 40-100-fold increase in its potency to stimulate purified soluble guan ylyl cyclase. Our data suggest that the biologic activity of ONOO- inv olves S-nitrosation of cellular thiols resulting in NO-mediated cyclic GMP accumulation.