Effect of 3-methylcholanthrene administration on hepatic ribonucleic acid polymerase activities.

The effect of the in vivo administration of 3-methylcholanthrene upon rat hepatic RNA polymerase activities was investigated. Aggregate RNA polymerase activity assayed in liver nuclei was stimulated by 33% over control. Characterization of the individual RNA polymerase activities by virtue of their differential sensitivity to alpha-amanitin revealed that RNA polymerase I activity was maximally increased by 70% at approx. 16 h post-administration of the polycyclic hydrocarbon; RNA polymerase II activity was stimulated by 33%. The kinetics of RNA polymerases I and II stimulation differed in that the nucleolar enzyme's activity increased earlier and peaked later. RNA polymerase III activity was not significantly different from control. Phenobarbital, another inducer of the mixed function oxidases, had essentially no effect on the activity of hepatic RNA polymerases. Solubilization of the RNA polymerases followed by separation on diethylaminoethyl (DEAE)-Sephadex allowed for a comparison of the treated and control enzymatic activities using a common exogenous template. While no qualitative difference was evident, RNA polymerases I and II isolated from 3-methylcholanthrene-treated rats again were more active than control, indicating an effect of the polycyclic hydrocarbon at the level of the enzyme.