Cardiovascular diseases have been the leading cause of death worldwide for many years. In recent years, new cardiovascular disease markers have been sought that can improve the diagnosis and treatment of this broad and prognostically unfavorable group of diseases. The efforts of many researchers are aimed at detecting changes in the level of enzymes in the lipid peroxidation system, which are antioxidants, as possible mechanisms underlying the development of cardiovascular disease. The imbalance between the intensification of free-radical oxidation caused by active oxygen forms and the activity of the body’s protective antioxidant system leads to serious disturbances: disorganization of cellular structures, changes in their functional activity. The article presents the study of the interrelation of the concentration distribution of enzymes of the lipid peroxidation system – antioxidants in blood serum and heart tissues of white non-pedigree rats. The correlation coefficients of Spearman, the gamma of correlation and Kendel Tau revealed a reliable presence of weak correlation between the concentration of glutathione peroxidase in blood serum and heart tissues (Spearman R = 0.18 at p ≤ 0.029408, Gamma = 0.14 at p ≤ 0.018701; Kendall Tau = 0.13 at p ≤ 0.018701).