Abstract

We have investigated the relationship between the capacity of rat liver microsomal preparations to metabolize several foreign substances, and their content of the carbon monoxide-binding pigment, P-450. A rapid and convenient radioactive assay for the hydroxylation of 3,4-benzpyrene has been developed and the kinetics of this system studied. Optically clear, but not soluble, enzyme preparations were obtained by treatment of rat liver microsomes derived from benzpyrene-treated animals with the nonionic detergent Triton N-101. It was shown that the capacity of these preparations to hydroxylate 3,4-benzpyrene after various types of treatments, was impaired in direct proportion to the conversion of P-450 to its inactive form, P-420. Benzpyrene hydroxylase activity and the content of P-450 during storage were conserved to a large degree by the addition of glycerol to the medium. Treatment of rats with either 3,4-benzpyrene or phenobarbital resulted in elevated levels of benzpyrene hydroxylase, zoxazolamine hydroxylase, and p-nitroanisole demethylase activities as well as in a higher P-450 content, although the increases of these various components resulting from drug treatment were not in the same proportion. Evidence for the reactivation of acid-treated enzyme preparations by the addition of flavins was obtained.