title: Cytochrome P-450 and halothane metabolism. Decrease in rat liver microsomal P-450 in vitro.
abstract: Anaerobic in vitro incubation of microsomes from phenobarbital(PB)-induced rats with halothane results in an irreversible decrease of measurable cytochrome P-450. There is a parallel decrease in heme content under the same incubation conditions. However, microsomes from 3-methylcholanthrene(3-MC)-induced or untreated animals do not show a reduction in cytochrome P-450 content. Aerobic incubation with halothane results in a decrease of cytochrome P-450 which can be completely reversed by dialysis or the addition of potassium ferricyanide. These latter treatments only partially restore the cytochrome P-450 levels following anaerobic incubations. The decrease in cytochrome caused by halothane is not associated with measureable heme N-alkyl adduct formation; lipid peroxidation does not play a role as indicated by the lack of effect of 1 mM EDTA or a decrease in glucose-6-phosphatase activity. Halothane metabolites are bound irreversibly to microsomal protein as determined by gel electrophoresis only when the oxygen concentration is very low. The mechanism of cytochrome P-450 decrease is consistent with the formation of a reactive metabolite which binds to the protein portion and also destroys heme.
mesh_terms: D000818:Animals; D002251:Carbon Tetrachloride / Q000633:toxicity; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D006221:Halothane / Q000378:metabolism* / Q000633:toxicity; D006418:Heme / Q000032:analysis; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D002251:Carbon Tetrachloride; D006221:Halothane