6533b837fe1ef96bd12a3121

RESEARCH PRODUCT

SEX DIFFERENCES IN THE PATTERN OF CYTOCHROMES P-450 IN RAT LIVER MICROSOMES

subject

description

ABSTRACT A number of sex differences in the spectral and enzymic properties of rat liver microsomes have been observed which may reflect differences in the population of hepatic cytochromes P 450 of male and female rats: 1. a blue shift in the spectrum of the reduced P 450-CO complex in females as compared to males, 2. lower ΔA max values in the binding of metyrapone to reduced microsomes in females as compared to males, 3. a higher proportion of 2-hydroxylation in the metabolism of biphenyl in females as compared to males, 4. preferential inhibition of ethoxycoumarin deethylation, benzpyrene hydroxylation and biphenyl-4-hydroxylation by α-naphthoflavone in females but by metyrapone in males. Sex differences are not abolished by a 36 h starvation period but level off after pretreatment of the animals with either 3-methylcholanthrene or phenobarbital. Since a blue shift in the CO spectrum, high proportion of 2-hydroxylation in the metabolism of biphenyl and preferential inhibition of monooxygenase activity by α-naphthoflavone are also characteristic for animals pretreated with polycyclic hydrocarbons we conclude that similarities exist in the population of hepatic microsomal cytochromes P 450 in untreated female rats and rats of both sexes pretreated with polycyclic hydrocarbons.