REGULATION OF CYTOCHROME-P450-2B1 2 MESSENGER-RNAS BY KEPONE(R) (CHLORDECONE) AND POTENT ESTROGENS IN PRIMARY CULTURES OF ADULT-RAT HEPATOCYTES ON MATRIGEL/

We previously reported that when primary cultures of rat hepatocytes w ere treated with phenobarbital (PB) or one of several organochlorine p esticides, including Mirex(R), there was co-induction of cytochrome P4 50 2B1 and 2B2 mRNAs and immunoreactive proteins, whereas Kepone(R) se lectively induced 2B2 (Kocarek et al. (1991) Mol. Pharmacol. 40, 203-2 10). Indeed, Kepone treatment actively suppressed induction of 2B1 and 2B2 mRNAs in hepatocytes cotreated with phenobarbital. Because Kepone differs chemically from Mirex only in the replacement of 2 chlorine a toms with a ketone group, which exists in aqueous solution as a gem-di ol and appears to confer weak estrogenic properties, we treated hepato cyte cultures with one of 3 potent estrogens, beta-estradiol, 17alpha- ethinylestradiol or diethylstilbestrol. Treatment with each of these e strogens induced 2B1 and 2B2 mRNA only at very high doses (10(-4) M). Beta-Estradiol (10(-4) M) treatment also induced 2B1/2 mRNA in hepatoc yte cultures prepared from a prepubescent female rat. The anti-estroge n tamoxifen failed to reverse 2B1/2 mRNA induction following beta-estr adiol or Kepone treatment of adult hepatocyte cultures. High doses of beta-estradiol or 17alpha-ethinylestradiol failed to induce 2B1/2 mRNA in treated rats. We also examined the effects of chloral hydrate, a s imple gem-diol, on 2B1/2 mRNA induction in the hepatocyte cultures. Tr eatment with chloral hydrate (3 x 10(-3) M), like Kepone (10(-5) M), s uppressed 2B1/2 mRNA induction following phenobarbital (10(-4) M) trea tment, while Kepone alcohol (10-5 M), which is not a gem-diol, produce d less suppression. Our results suggest that selective induction by Ke pone of 2B2 is unlikely related to its effects as a weak classical est rogen, while the ability of Kepone to suppress induction of 2B1 and 2B 2 by PB may be related to its properties as a gem-diol.