The purpose of the study, therefore, was to investigate the content of substances of low and medium molecular weight, total and tyrosine-containing peptides and to assess the level of endogenous intoxication of the rat organism under conditions of experimental nephropathy and the use of reduced glutathione. Materials and methods. The experiment was performed on nonlinear white rats weighing 160-180 g. The animals were in a vivarium with a constant temperature (18-22°C), relative humidity (50-55%) in individual exchange cells in the formed groups, on a constant balanced mode of a diet with free access to water and food. Nephropathy was modeled by a single intraperitoneal injection of folic acid at a dose of 250 mg/kg. Glutathione was administered intragastrically (100 mg/kg) for 7 days after folic acid intoxication. Results and discussion. Under conditions of nephropathy in the blood serum of rats, an increase in the level of molecules of average weight was observed by 2 times, as well as low-molecular substances by 1.6 times compared with the control. Daily administration of reduced glutathione to animals with nephropathy for 7 days led to a decrease in the level of substances of medium and low molecular weight by 21% and 27% in comparison with the indicators of animals with nephropathy, but still significantly differed from the control indicators. Against the background of an increase in the content of total oligopeptides by 2.2 times in the blood serum of experimental rats, the level of tyrosine-containing peptides increased by 1.8 times in comparison with the control. The introduction of glutathione to rats with nephropathy led to a decrease in these parameters by 40 and 35%, respectively, compared with the experimental control. As a result of the established changes in the level of albumin and average weight molecules in the blood serum of animals, under conditions of nephropathy, an increase in the coefficient of endogenous intoxication was observed by 2.3 times. This imbalance indicates a violation of the processes of detoxification of endogenous metabolites in the liver of animals under conditions of nephropathy. In the groups of animals with nephropathy, which were injected with an antioxidant, the coefficient of endogenous intoxication decreased by 41% compared with animals that did not receive glutathione, but this indicator did not return to the level of control values. Conclusion. Thus, under the conditions of experimental nephropathy in the blood serum of rats, an increase in the content of total and tyrosine-containing peptides, substances of low and medium molecular weight, as well as an increase in the values of the intoxication coefficient was observed, which indirectly indicates a violation of the processes of detoxification of endogenous metabolites in the liver of experimental animals with kidney pathology. In the group of animals with nephropathy that received reduced glutathione for 7 days, only a tendency towards normalization of the studied parameters characterizing the level of endogenous intoxication under conditions of nephropathy was noted