Effects of Dibutyryl Adenosine 3′,5′-Monophosphate, Angiotensin II, and Atrial Natriuretic Factor on Phosphorylation of a 17,600-Dalton Protein in Adrenal Glomerulosa Cells

Rat adrenal glomerulosa cells were incubated with [32P]phosphate and (Bu)2AMP (dbcAMP), angiotensin II, and atrial natriuretic factor (ANF). Incorporation of [32P]phosphate into cellular proteins was analyzed by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. dbAMP stimulated phosphorylation of a 17.6K protein, while angiotensin II did not stimulate it. ANF did not affect the protein phosphorylation, whether the cells were in the basal state or stimulated by dbcAMP or angiotensin II. On the other hand, ANF markedly inhibited angiotensin II-stimulated aldosterone production, but only slightly inhibited dbcAMP-stimulated aldosterone. These results suggest that in rat adrenal glomerulosa cells phosphorylation of the 17.6K protein may have a relationship with the stimulatory effect of cAMP on aldosterone production; however, neither angiotensin II nor ANF affected the phosphorylation of this protein, and phosphorylation of the 17.6K protein is not an obligatory step in the regulation of aldosterone production.