Halothane and isoflurane inhibit endothelium-dependent relaxation elicited by acetylcholine

The purpose of this study was to determine whether volatile anesthetics modify the release of endothelium-derived relaxing factor. We examined the effects of halothane and isoflurane on endothelium-dependent relaxation and 3',5'-cyclic guanosine monophosphate formation elicited by acetylcholine and ionophore A23187 in isolated rat aorta. Halothane and isoflurane (1%-2%) significantly attenuated acetylcholine-induced relaxation of the phenylephrine-contracted aorta but had no significant effect on relaxation induced by A23187, nitroprusside, and nitroglycerin. Basal and A23187 (10(-7) M)-stimulated levels of 3',5'-cyclic guanosine monophosphate were slightly lowered by halothane and isoflurane (2%). In contrast, the increase of 3',5'-cyclic guanosine monophosphate elicited by acetylcholine (10(-5) M) was significantly attenuated by halothane (2%) and abolished by isoflurane (2%). These findings indicate that halothane and isoflurane strongly inhibit the release of endothelium-derived relaxing factor elicited by acetylcholine.