Role of cytoplasmic proteins in the process of thyroxine stimulation of protein phosphorylation in rat liver and brain

: The role of thyroxin and thyroxin action modulator (cytoplasmic protein mediating some hormonal effects on the mitochondria and nucleus) in rat liver and brain protein phosphorylation was studied in experiments. In the liver, an organ sensitive to thyroid hormones, the modulator was found to stimulate the activity of specific protein kinases contributing to protein phosphorylation, and co-incubation of physiologic concentrations of T4 with the modulator enhanced the stimulatory effect. In the brain change of the thyroid status did not change the protein kinase activation. Incubation of T4 and thyroxin effect modulator did not change the enzymic activity either.