Administration of 3-methylcholanthrene to rats increases the specific hybridizable mRNA coding for cytochrome P-450c.

Abstract

Poly(A)+-RNA obtained from the livers of 3-methylcholanthrene (3MC)-treated rats was translated into cytochrome P-450c in a cell-free reticulocyte system. In this translational system, no precursor cytochrome P-450c was observed. The mRNA responsible for the synthesis of this cytochrome was isolated by immunoprecipitation of liver polyribosomes obtained 15 h after 3MC treatment, and a c[complementary]DNA was constructed by the reverse transcriptase reaction. The cDNA was further purified by hybridizing at a high R0t (product of RNA concentration and incubation time) to poly(A)+-RNA isolated from control rat liver, and the nonhybridized, single-stranded cDNA was isolated by hydroxylapatite chromatography. This cDNAP-450c was employed in hybridization reactions with poly(A)+-RNA isolated from the livers of rats treated with 3MC for various times. These studies indicated a maximal induction of mRNAP-450c at about 15 h after 3MC injection, although levels of this mRNA were significantly increased by 7 h. The mRNAP-450c concentration had diminished by 24 h but remained higher than control levels for at least 48 h. 3MC apparently has an effect on the accumulation of mRNAP-450c in rat liver.