Effects of phorbol ester on catecholamine secretion and protein phosphorylation in adrenal medullary cell cultures.
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 approximately 70% at 0.5 microM Ca2+ and 30% at 10 microM Ca2+. PMA enhanced the maximal response to Ca2+ approximately 25% and decreased the Ca2+ concentration required for half-maximal secretion approximately 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.
Pocotte
S L
SL
Frye
R A
RA
Senter
R A
RA
TerBush
D R
DR
Lee
S A
SA
Holz
R W
RW
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D002837:Chromaffin Granules / Q000378:metabolism; D002855:Chromatography, Thin Layer; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004987:Ethers / Q000494:pharmacology; D015759:Ionomycin; D008970:Molecular Weight; D009638:Norepinephrine / Q000378:metabolism*; D010704:Phorbols / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004987:Ethers; D010704:Phorbols; D011506:Proteins; D015759:Ionomycin; D011494:Protein Kinases; D011493:Protein Kinase C; D004072:Digitonin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D009638:Norepinephrine