Effects of 3,4-benzpyrene, phenobarbital, and chlordane on the nucleic acid and protein content of subfractions of rat liver homogenates

Abstract

3,4-Benzpyrene, phenobarbital, and chlordane are three compounds that produce marked increases in the activities of hepatic microsomal drug-metabolizing enzyme systems. They were compared with regard to their effects on the nucleic acid and protein content of various subfractions of rat liver homogenates. Pretreatment of rats with chlordane and phenobarbital produced similar changes. The changes produced by pretreatment with 3,4-benzpyrene, however, differed from those of phenobarbital and chlordane. The differences between the effects of 3,4-benzpyrene and those of chlordane and phenobarbital were noted primarily in the subfractions of rat liver homogenates which contained largely smooth endoplasmic reticulum (SER). Chlordane and pheno-barbital caused significantly greater increases than 3,4-benzpyrene in the RNA and protein content of the fraction containing the SER. Pretreatment with each of the three compounds produced statistically significant decreases in DNA content of liver homogenates when expressed as mg DNA/g liver. Considered in the light of previously accumulated evidence, the results provided further support for the hypothesis that 3,4-benzpyrene may exert its stimulatory effects on hepatic microsomal drug-metabolizing enzyme systems through a mechanism different from that of phenobarbital and chlordane.