Does halothane or isoflurane affect hypoxic and post-hypoxic vascular response in rabbit aorta?

Abstract

Halothane and isoflurane affect differently endothelium-dependent and -independent vasorelaxation at 95% O2. In addition, hypoxic vascular response might involve endothelium-dependent and -independent mechanisms. Therefore, we investigated, in rabbit aortic rings, 1) the influence of halothane and isoflurane on vasodilation at 95% O2 and on hypoxic-induced vasorelaxation at 0% O2 and 2) the influence of halothane and isoflurane on endothelium-dependent and -independent post-hypoxic vascular response. Endothelium-intact and endothelium-denuded rabbit aortic rings were used. Phenylephrine precontracted rings were exposed, at 95% O2, to acetylcholine (ACh, 10(-9) to 10(-4) M) or sodium nitroprusside (SNP, 10(-9) to 10(-4) M) in the presence or absence of anaesthetic at 1 or 2 MAC. Precontracted rings were also exposed to an acute reduction in O2 from 95% to 0% followed by an acute reoxygenation with 95% O2 in the absence or presence of anaesthetic at 1 or 2 MAC. At 95% O2, halothane decreased endothelium-dependent relaxation to ACh, while endothelium-independent relaxation to SNP was decreased only at 2 MAC. Isoflurane did not modify ACh- or SNP-induced relaxation. At 0% O2, neither halothane nor isoflurane altered the hypoxic vascular relaxation. Post-hypoxic response was not changed either. Our results indicate that halothane and isoflurane do not alter vascular hypoxic response in conductance arteries.