The incorporation of 32PO4 into cytosol and ribosomal proteins was measured after cAMP and ACTH treatment of functional adrenal tumor cell cultures. Although small changes in total 32PO4 uptake occurred after ACTH treatment a marked increase in 32PO4 incorporation into cytosol and ribosomal proteins was observed. Changes in phosphate uptake and pool size previously observed after cAMP treatment were eliminated by the use of preincubated adrenal cell cultures. In the absence of such changes, selective increases in the incorporation of 32PO4 into cytosol and ribosomal protein were observed after cAMP treatment. This is the first report that cAMP increases the phosphorylation of both cytosol and ribosomal proteins. These results support the concept that ACTH regulates adrenal cell function via cAMP dependent phosphorylation of adrenal cell proteins.
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