[Changes in RNA synthesis at early stages of aminoazocancerogenesis]

A single injection of the carcinogen 3'-methyl-4-dimethylaminoazobenzene (3'MDAB) or its non-carcinogen analogue 2-methyl-4-dimethylaminoazobenzene (2-MDAB) 300 mg/1000 g body weight led to the increase in the RNA-synthetic capacity of liver cell nuclei in vitro. No differences were found in the ribonuclease activity; in the template activity of DNA and DNP with E. coli RNA-polymerase, and in the melting temperature of DNA and DNP in the presence of 3'MDAB and in the control. The apparent value or Km of the RNA synthesis reaction are equal both for the control animals and those treated with 3'MDAB, but Vmax is lower in the control. It is suggested that the increase of RNA synthetic capacity of the nuclei of rat liver cells, found in vitro at early stages of the carcinogen (3'MDAB) action, should be regarded as the manifestation of its toxic effect and is proposed to be due to the increase of the concentration of RNA-polymerase which is capable to catalyse the RNA synthesis in nuclei.