[Effect of thyroid hormones on heat-induced changes in the EPR-spectra of erythrocytes].

An increase in the fluidity of membranes in experimental hyperthyreosis of rats was shown by the registration of EPR-signals labeled with spin probe (5-dosilsterate). Modifications of the physical state of erythrocytic membranes induced in vivo by thyroid hormones were shown to depend on the fatty acid composition of food fats. Thus, the simulation of hyperthyreosis against a background of a diet with more viscous fats (pork lard) was accompanied by a decrease in the fluidity of erythrocytic membranes, whereas food enrichment with polyunsaturated fats (sunflower oil) inhibited the effect of hyperthyreosis on the structural state of membranes. An increase in the fluidity of membranes also resulted from the incubation of erythrocytes of normal animals with physiological concentrations of triiodothyronine (10(-9) M). Under these conditions adding up of thyroxine (10(-7) M) prevented the effect of the first hormone on the structure of membranes. It was assumed that a modifying effect of thyroid hormones in vivo was partially based on rearrangements in the fatty acid composition of membrane lipids.