Isoflurane enhances dechlorination of carbon tetrachloride in guinea-pig liver microsomes

Preventive effect of isoflurane on destruction of cytochrome P450 during reductive dehalogenation of carbon tetrachloride in guinea-pig liver microsomes

Effects of isoflurane on cytochrome P450 loss during anaerobic dechlorination of carbon tetrachloride in guinea pig liver microsomes were examined. Under anaerobic conditions, chloroform was produced from carbon tetrachloride by the microsomes in the presence of NADPH, and production of chloroform was increased 1.80 times by the addition of isoflurane. The concentration of microsomal cytochrome P450 decreased to 71.6% after 7 minutes incubation with carbon tetrachloride and NADPH. With the addition of isoflurane in the same incubation system, the decrease in cytochrome P450 was to 84.9%. The essential components for the loss of cytochrome P450 during the dechlorination of carbon tetrachloride were microsomes, NADPH and carbon tetrachloride. Addition of carbon monoxide reduced the cytochrome P450 loss to negligible. These findings indicate that isoflurane interacts with cytochrome P450 to prevent the cytochrome P450 destruction during the anaerobic dechlorination of carbon tetrachloride in guinea-pig liver microsomes. These results also suggest that the destruction of cytochrome P450 during anaerobic dechlorination of carbon tetrachloride in microsomes was caused by direct attack by the trichloromethyl radical, rather than by carbon tetrachloride-induced lipid peroxidation.

Stimulatory effect of anesthetics on dechlorination of carbon tetrachloride in guinea-pig liver microsomes

Effects of the anesthetics isoflurane, enflurane, halothane and sevoflurane on the dechlorination of carbon tetrachloride to produce chloroform were investigated using guinea pig liver microsomes. Under anaerobic conditions, chloroform is produced from carbon tetrachloride by the microsomes in the presence of NADPH, and chloroform production from 86 microM carbon tetrachloride was enhanced to 146%, 133%, 123% and 115% by the addition of isoflurane, enflurane, halothane and sevoflurane, respectively. The half-life of oxidized cytochrome P450 which remained during the reduction by the addition of NADPH was shortened to 51%, 54%, 60% and 80% by isoflurane, enflurane, halothane and sevoflurane, respectively, without alteration of NADPH-cytochrome c reductase activity. These anesthetics hastened the onset of the 445 nm absorption band formation which was shown by microsomes with carbon tetrachloride in the presence of NADPH under anaerobic conditions. These results indicate that the anesthetics isoflurane, enflurane, sevoflurane and halothane stimulate the reduction of cytochrome P450 results in the acceleration of the carbon tetrachloride dechlorination. These results may have implications for other type II drugs that are administered during anesthesia.