Action of halothane upon mitochondrial respiration

The inhibitory action of halothane upon respiration was studied with rat liver mitochondria (RLM³), beef heart mitochondria (HBHM), and electron-transport particles (ETP). With intact mitochondrial preparations the oxidation of NADH-linked substrates but not of succinate was markedly suppressed by low concentrations of halothane (<2 mm as determined by gas-liquid chromatography). This inhibitory action of halothane was completely reversible. In contrast, a number of other mitochondrial processes were found to be sensitive in an irreversible manner at higher concentrations of the anesthetic. Likewise, the oxidation of added NADH by HBHM, ETP, and detergent-disrupted RLM was found to be sensitive in a reversible manner to low concentrations of halothane. The energy-dependent transfer of electrons from succinate to NAD by ETP_H was also sensitive to halothane. On the other hand, the NADH-ferricyanide reductase and the succinic oxidase activities of ETP and the NADH-cytochrome c reductase activity of microsomes were all insensitive to halothane. The site of inhibition by halothane appears to be in the vicinity of the rotenone-sensitive site of complex I (NADH-CoQ reductase). A number of other general anesthetics inhibited respiration at or near the same site as halothane.