Effects of Phorbol Ester on Catecholamine Secretion and Protein Phosphorylation in Adrenal Medullary Cell Cultures

• Published in: Proceedings of the National Academy of Sciences - PNAS 1985-02, Vol.82 (3), p.930-934
• Main Authors: Pocotte, Susan L., Frye, Roy A., Senter, Ruth A., TerBush, Daniel R., Lee, Sung A., Holz, Ronald W.
• Format: Article
• Language: English
• Subjects: Adrenal Medulla - drug effects; Adrenal Medulla - metabolism; Animals; Biological and medical sciences; Calcium - metabolism; Catecholamines; Cattle; Cell membranes; Cell physiology; Cells, Cultured; Chromaffin cells; Chromaffin Granules - metabolism; Chromatography, Thin Layer; Digitonin - pharmacology; Dose-Response Relationship, Drug; Electrophoresis; Enzymes; Ethers - pharmacology; Exocytosis; Fundamental and applied biological sciences. Psychology; Gels; Ionomycin; Molecular and cellular biology; Molecular Weight; Norepinephrine - metabolism; Phorbols - pharmacology; Phosphorylation; Protein Kinase C; Protein Kinases - metabolism; Proteins - metabolism; Secretion; Secretion. Exocytosis; Tetradecanoylphorbol Acetate - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.82.3.930

The effects of phorbol 12-myristate 13-acetate (PMA) on catecholamine secretion and protein phosphorylation from intact and digitonin-treated chromaffin cells were investigated. PMA (10-300 nM), an activator of protein kinase C, caused a slow Ca2+-dependent release of catecholamine from intact chromaffin cells that was potentiated by the Ca2+ionophore ionomycin. PMA also enhanced secretion induced by Ba2+. In cells with plasma membranes rendered permeable by digitonin to Ca2+, ATP, and protein, PMA (100 nM) enhanced Ca2+-dependent secretion ≈ 70% at 0.5 μ M Ca2+and 30% at 10 μ M Ca2+. PMA enhanced the maximal response to Ca2+≈ 25% and decreased the Ca2+concentration required for half-maximal secretion ≈ 30%. The effects of PMA on chromaffin cells were associated with a 2- to 3-fold increase in the phosphorylation of a 56-kDa protein that may be tyrosine hydroxylase. Other proteins were phosphorylated to a lesser extent. The experiments suggest that PMA increases protein kinase activity and secretion in chromaffin cells and raise the possibility that protein kinase C modulates catecholamine secretion in chromaffin cells.