[Effect of ACTH on protein phosphorylation in rat adrenal ribosomes]

The authors studied the influence of ACTH on the steroidogenesis and 32P-labeled KH2PO4 incorporation into the ribosome proteins under conditions of incubation of the rat adrenal glands in vitro. 30 minutes before the incubation ACTH added into the medium stimulated corticosteroid biosynthesis by 116 +/- 26% and increased the radioactive phosphorus incorporation into the sum total ribosome proteins by 38 +/- 7%. Ribosome proteins were separated by electrophoresis in polyacrylamide gel at pH 4.5 into 30 fractions. 5--6 protein fractions proved to be phosphorylated during the incubation. ACTH altered the phosphorylation of individual protein fractions differently: there was stimulation in 2 fractions and inhibition of phosphorylation--in 3. It was revealed that, along with steroidogenesis, ACTH altered the phosphorylation of ribosome proteins. The change of the rate of ribosome phosphorylation was possibly one of the mechanisms with the aid of which the steroidogenic action of ACTH is realized.