Role of protein kinase C in catecholamine secretion from digitonin-permeabilized bovine adrenal medullary cells.
The effects of staurosporine and K-252a, potent inhibitors of protein kinases, and 12-O-tetradecanoylphorbol-13-acetate (TPA) on catecholamine secretion and protein phosphorylation in digitonin-permeabilized bovine adrenal medullary cells were investigated. Staurosporine and K-252a (0.01-10 microM) did not cause large changes in catecholamine secretion evoked by Ca2+ in digitonin-permeabilized cells whereas these compounds strongly prevented TPA-induced enhancement of catecholamine secretion in a concentration-dependent manner. Incubation of digitonin-permeabilized cells with [gamma-32P]ATP resulted in 32Pi incorporation into a large number of proteins, detected as several major bands and darkened background in autoradiograms. Ca2+ and TPA increased phosphorylation of these proteins. Staurosporine and K-252a markedly inhibited Ca(2+)-induced and TPA-induced increases in protein phosphorylation as well as basal (0 Ca2+) protein phosphorylation in digitonin-permeabilized cells. Long term treatment (24 h) of adrenal medullary cells with 1 microM TPA markedly decreased total cellular protein kinase C activity to about 5.3% of control. Pretreatment of the cells with 1 microM TPA strongly inhibited the TPA-induced enhancement of catecholamine secretion whereas it did not cause large changes in total cellular catecholamine amounts, Ca(2+)-induced catecholamine secretion, and cAMP-induced enhancement of catecholamine secretion from digitonin-permeabilized cells. From these results we conclude that protein kinase C plays a modulatory role in catecholamine secretion rather than being essential for initiating catecholamine secretion.
Isosaki
M
M
Department of Pharmacology, Nara Medical University, Kashihara, Japan.
Nakashima
T
T
Kurogochi
Y
Y
D000313:Adrenal Medulla / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism*; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D004072:Digitonin / Q000494:pharmacology; D026121:Indole Alkaloids; D007700:Kinetics; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D002227:Carbazoles; D002395:Catecholamines; D026121:Indole Alkaloids; C049985:staurosporine aglycone; D011493:Protein Kinase C; D019311:Staurosporine; D004072:Digitonin; D013755:Tetradecanoylphorbol Acetate