The role of DNA-dependent RNA polymerases in microsomal enzyme induction in southern armyworm ( Spodoptera eridania) larvae

Abstract

RNA polymerase activity in a midgut nuclear fraction from southern armyworm larvae exposed to the microsomal enzyme inducer pentamethylbenzene (PMB, 2000 ppm in diet) was 40% higher than in controls. With the solubilized, partially purified polymerases, the activity of RNA polymerase III increased about 40% in response to the inducing action of PMB; polymerase II activity was only slightly enhanced in induced larvae and no change was observed in the activity of polymerase I. Treatment of larvae with α-amanitin (0.25 μg/larva) or cycloheximide (50 ppm in diet) caused respectively a 60% and 70% reversal of the PMB-induced increase in RNA polymerase activity. Such treatments also cause an essentially complete block of the PMB induction of microsomal N- demethylase and NADPH-cytochrome c reductase. The data are discussed in relation to the involvement of the transcription process in the mechanism of microsomal enzyme induction.