Alteration in hepatic nuclear RNA polymerase activity following benzo[a]pyrene administration in rat

Benzo[a]pyrene was administered intraperitoneally to male Wistar rats as a single dose of 20 mg.kg-1 body weight. Two hours after its administration, livers were excised and the enzyme RNA polymerase was solubilized from purified nuclei. The enzyme was resolved into three forms, polymerase I, II and III by partial purification on DEAE-Sephadex A-25 column. All the three forms of nuclear RNA polymerase were inhibited in response to administration of benzo[a]pyrene. This was evident in terms of total yield as well as specific activity of each enzyme. The inhibition of nuclear transcription following administration of benzo[a]pyrene as observed previously (1) along with the present results on the enzyme inhibition clearly suggest that benzo[a]pyrene acts on both the major components of transcription machinery i.e. the template chromatin and the enzyme RNA polymerases.