Mechanisms of occurence of oxidative stress in erythrocytes of tumor-bearing organism

The development of neoplasm in the body is accompanied by activation of lipid peroxidation and changes in enzyme activity level in peripheral blood erythrocytes. Oxidative stress is caused by the accumulation of intermediate metabolites in erythrocytes, as a result of tumor impact on the body. Thus, the activation of free radical oxidation is a standard efferent link of the systemic tumor effect. There is no consensus regarding the activity and role of antioxidant enzymes in the oxidative stress during the development of neoplasms. The purpose of our study was to evaluate the impact of the enzymatic link of the antioxidant and glutathione systems on the oxidative stress in red blood cells of rats with transplanted ovarian ascitic tumor. Materials and Methods. The work was performed on the erythrocytes of mongrel white rats with transplanted ascitic ovarian tumor, assessed in stationary and terminal phases of tumor growth. The levels of malondialdehyde, diene conjugates, ketodienes, Schiff bases, activity of glutathione reductase, Glu-tathione-S-transferase, glutathione peroxidase, and levels of reduced and oxidized glutathione were determined biochemically in the erythrocyte hemolysate. Results. We observed a significant increase in the levels of malondialdehyde and diene conjugates, as well as superoxide dismutase, catalase and Glutathione-S-transferase activity in tumor-bearing rats compared to the controls. The activity of glutathione peroxidase, reduced glutathione levels and the ratio of reduced and oxidized glutathione decreased. Conclusion. Our data suggests the depletion of reduced glutathione pool as a result of decrease in its formation and enhanced activity of Glutathione-S-transferase under increased lipid peroxidation in red blood cells of tumor-bearing rats.