Changes in cytochrome P450 molecular species in rat liver in chloroform intoxication

The effect of CHCl3 on the composition of hepatic microsomal cytochrome P450 species was compared with that of CCl4 in rats pretreated with phenobarbital (PB) or 3-methylcholanthrene (3MC). The administration of CHCl3 hardly affected cytochrome P450 content in non-treated rat liver, but caused a similar degree of depletion in the content as observed after CCl4 administration in PB-pretreated rats. In the pretreatment with 3MC, the administration of CHCl3 brought about a marked decrease in the content to 24% of control after 12 hr, while CCl4 reduced the content only to one-half of control. It was demonstrated by SDS-polyacrylamide gel electrophoresis and Whatman DE-52 anion-exchange chromatography that 3MC-induced P450 species decreased with CHCl3, while it was affected little by CCl4 treatment. The activity of benzo[a]pyrene hydroxylase was altered together with the change in the content of cytochrome P450 species. The administration of CHCl3 to PB-pretreated rats caused the depletion in PB-induced P450. These findings indicate that cytochrome P450 species induced with 3MC as well as PB are highly susceptible to CHCl3 intoxication, whereas the administration of CCl4 depletes the PB-induced species without affecting the 3MC-induced species.