[Generation of superoxide anion-radical in the liver monooxygenase system of preliminary radiation-exposed tumor-bearing rats].

Generation of superoxide anion-radical (O2*-) in reductase and oxygenase electron-transport chains in the liver monooxygenase system was investigated in tumor-bearing rats exposed to preliminary irradiation. Preliminary irradiation of rats (before transplantation of Guerin's carcinoma) resulted in the increased generation of superoxide anion-radical by components of the liver monooxygenase system in the logarithmic phase of oncogenesis. It is shown that the increased NADPH-cytochrome P-450 reductase activity is accompanied with the intensification of superoxide anion-radical generation in liver microsomal fraction of preliminary radiation-exposed rats. At the same time the cytochrome P-450 hydroxylase activity in the microsomal fraction of tumor-bearing rats subjected to preliminary irradiation was decreased.