[Effect of thyroxine on methemoglobin content and the activity of antioxidant enzymes of human erythrocytes in vitro].

A study was made of the effect of thyroxine in vitro on the activity of antioxidant enzymes: superoxide dismutase (SOD) and catalase, and on the methemoglobin content in the erythrocytes of 23 healthy persons aged 17-25. Erythrocyte incubation was performed in different media: in their own plasma, a weak solution of NaOH, tris-HCl buffer solution (pH 7.4) with thyroxine in the physiological concentration and without it. The enzyme activity was compared in the native and incubated erythrocytes. After the incubation of erythrocytes with thyroxine in their own plasma the SOD and catalase activity showed a statistically significant rise, and the methemoglobin content decreased. This effect was undetectable in the incubation of erythrocytes with thyroxine in tris-buffer solution. Direct incubation of SOD with thyroxine isolated from the erythrocytes did not cause any changes in enzyme activity. Probably the interaction of thyroxine with erythrocyte membrane components is important for the implementation of the hormonal effect. Some unidentified factors contained in the blood plasma may play a role in the SOD activation. The authors discuss thyroxine ab to cause rapid regulation of the activity antioxidant enzymes.