[Factors reducing the superoxide dismutase activity of the liver of rats with Pliss lymphosarcoma].

The procedures for isolation and purification of Cu/Zn superoxide dismutase (SOD) from small amounts of rat liver at different stages of Pliss lymphosarcoma growth were developed. Two stages of tumour growth were distinguished. At the first stage (4-5th day after reinoculation) the intensity of optical (680 nm) and EPR spectra of SOD was decreased, on the average, to 30%, while at the second stage--by 40% at 680 nm and by 32%, at 260 nm. The intensity of the EPR spectra was also diminished by 40% as compared to the control. It was assumed that at initial stages of tumour growth the decrease of the SOD activity is mainly due to the reduction of enzyme Cu, while at the second stage--to the decrease of the protein content. In all probability, the observed changes are induced by the activation of lipid peroxidation involving active O2 species. The second stage is associated with the superoxide-induced impairment of the function of nucleic acids involved in protein biosynthesis.