Differences in the constitutive forms of hepatic cytochrome p-450 in male and female adult beagle dogs

Abstract

Cytochrome P-450 isoenzymes were prepared from the solubilized liver microsomes of untreated adult male and female dogs, then separated into groups by high-performance liquid chromatography (HPLC). Partial purification was also completed through DEAE-53 cellulose and phosphocellulose ion-exchange chromatography. For comparison, solubilized hepatic cytochromes P-450 were obtained from rats dosed with phenobarbital (PB), β-naphthoflavone (BNF) or pregnenolene-16 α-carbonitrile. Minimal molecular masses of cytochrome P-450 subpopulations were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. HPLC and ion-exchange chromatography results suggested the presence of two or three major and several minor cytochrome P-450 subpopulations. Three distinct groups were predominant in the female and two major and two or three minor subpopulatins were found in the male. One of two isoenzymes prominent in BNF-dosed rats were present in the male but was missing in the female dog; another minor canine cytochrome similar to one found in PB-dosed rats was missing from the male. These data indicate qualitative and quantitative sex-dependent differences in the constitutive cytochrome P-450 populations of the dog and suggest that HPLC analysis may be useful for the interpretation of toxicology studies were microsomal enzyme induction is suspected.