Glutathione causes coronary vasodilation via a nitric oxide- and soluble guanylate cyclase-dependent mechanism

The actions of thiols on coronary vascular tone in the intact heart are unknown. Glutathione (GSH), glutathione disulfide (GSSG), and L-cysteine (10-1,000 mu M each) and GSH ethyl ester (8-300 mu M) were infused into isolated rat hearts perfused with Krebs buffer at a constant pressure by the Langendorff method. GSH, GSSG, and GSH ethyl ester, but not L-cysteine, caused a concentration-dependent increase in coronary flow with the following order of potency: GSH ethyl ester > GSH = GSSG. The nitric oxide synthase inhibitor N-G-monomethyl-L-arginine (300 mu M), prevented the increase in coronary flow with GSH and attenuated that with GSSG (300 mu M each). The vasodilation with GSH or GSSG and the associated increase in myocardial guanosine 3',5'-cyclic monophosphate were abolished by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1- one (a specific inhibitor of soluble guanylate cyclase) at 1 and 3 mu M, respectively. The vasodilator action of GSH was abolished by superoxide dismutase (50 U/ml). Inhibition of GSH reductase abolished GSSG-induced vasodilation. Neither glibenclamide (1 mu M) nor indomethacin (4 mu M) affected the vasodilator action of GSH and GSSG. We conclude that GSH and GSSG cause coronary vasodilation that is mediated by a nitric oxide-and guanylate cyclase-dependent mechanism, possibly mediated by the reaction between GSH and peroxynitrite to form S-nitrosoglutathione, a nitric oxide donor.