Hanley Peter J, Ray John, Brandt Ulrich, Daut Jürgen
Institut für Normale und Pathologische Physiologie der Universität Marburg, Deutschhausstrasse 2, Germany.
J Physiol. 2002 Nov 1;544(3):687-93. doi: 10.1113/jphysiol.2002.025015.
We have investigated the effects of volatile anaesthetics on electron transport chain activity in the mammalian heart. Halothane, isoflurane and sevoflurane reversibly increased NADH fluorescence (autofluorescence) in intact ventricular myocytes of guinea-pig, suggesting that NADH oxidation was impaired. Using pig heart submitochondrial particles we found that the anaesthetics dose-dependently inhibited NADH oxidation in the order: halothane > isoflurane = sevoflurane. Succinate oxidation was unaffected by either isoflurane or sevoflurane, indicating that these agents selectively inhibit complex I (NADH:ubiquinone oxidoreductase). In addition to inhibiting NADH oxidation, halothane also inhibited succinate oxidation (and succinate dehydrogenase), albeit to a lesser extent. To test the hypothesis that complex I is a target of volatile anaesthetics, we examined the effects of these agents on NADH:ubiquinone oxidoreductase (EC 1.6.99.3) activity using the ubiquinone analogue DBQ (decylubiquinone) as substrate. Halothane, isoflurane and sevoflurane dose-dependently inhibited NADH:DBQ oxidoreductase activity. Unlike the classical inhibitor rotenone, none of the anaesthetics completely inhibited enzyme activity at high concentration, suggesting that these agents bind weakly to the 'hydrophobic inhibitory site' of complex I. In conclusion, halothane, isoflurane and sevoflurane inhibit complex I (NADH:ubiquinone oxidoreductase) of the electron transport chain. At concentrations of approximately 2 MAC (minimal alveolar concentration), the activity of NADH:ubiquinone oxidoreductase was reduced by about 20 % in the presence of halothane or isoflurane, and by about 10 % in the presence of sevoflurane. These inhibitory effects are unlikely to compromise cardiac performance at usual clinical concentrations, but may contribute to the mechanism by which volatile anaesthetics induce pharmacological preconditioning.
我们研究了挥发性麻醉剂对哺乳动物心脏电子传递链活性的影响。氟烷、异氟烷和七氟烷可使豚鼠完整心室肌细胞中的NADH荧光（自发荧光）可逆性增加，提示NADH氧化受损。利用猪心脏亚线粒体颗粒，我们发现麻醉剂按以下顺序剂量依赖性抑制NADH氧化：氟烷＞异氟烷 = 七氟烷。琥珀酸氧化不受异氟烷或七氟烷影响，表明这些药物选择性抑制复合体I（NADH：泛醌氧化还原酶）。除抑制NADH氧化外，氟烷还抑制琥珀酸氧化（以及琥珀酸脱氢酶），尽管程度较轻。为检验复合体I是挥发性麻醉剂作用靶点这一假说，我们使用泛醌类似物DBQ（癸基泛醌）作为底物，研究了这些药物对NADH：泛醌氧化还原酶（EC 1.6.99.3）活性的影响。氟烷、异氟烷和七氟烷剂量依赖性抑制NADH：DBQ氧化还原酶活性。与经典抑制剂鱼藤酮不同，这些麻醉剂在高浓度时均未完全抑制酶活性，提示它们与复合体I的“疏水抑制位点”结合较弱。总之，氟烷、异氟烷和七氟烷抑制电子传递链的复合体I（NADH：泛醌氧化还原酶）。在约2 MAC（最低肺泡浓度）时，存在氟烷或异氟烷时NADH：泛醌氧化还原酶活性降低约20%，存在七氟烷时降低约10%。这些抑制作用在通常临床浓度下不太可能损害心脏功能，但可能有助于解释挥发性麻醉剂诱导药理学预处理的机制。
