The regulation of the nuclear RNA polymerase activity of the liver and brain in rats of different ages by a cytoplasmic modulator of thyroxine action

: The effect of physiological, concentration of thyroxine and cytoplasm thyroxine-binding protein (thyroxine action modulator, TAM4) on the RNA-polymerase activity in rat liver and bain cells in ontogenesis was studied. The physiological doses of the hormone were shown not to effect the RNA-polymerase of isolated liver and brain nuclei, while TAM4 caused the stimulation of enzymatic activity in these organs. ++TAM4 stimulating effect in liver correlated with increasing animal age, while the maximum RNA-polymerase activation by tAM was discovered in young rats under one month-At later stage the RNA-polymerase activity was same as in the controls. In is suggested that the cytoplasmic hormone-binding proteins take part in the formation of liver and brain sensitivity to the action of the thyroid gland hormones.