Pharmacological study on Ba2(+)-stimulated catecholamine secretion from cultured bovine adrenal chromaffin cells: possible relation of Ba2+ action to Ca(2+)-activated secretory mechanism.
The stimulatory action of Ba2+ on catecholamine secretion from cultured bovine adrenal chromaffin cells was studied to elucidate a possible relationship between Ba2+ action and the Ca2(+)-mediated secretory mechanism. Catecholamine secretion was dramatically stimulated by Ba2+ in the absence of external Ca2+, and this stimulatory action was observed in a concentration-dependent manner. Ba2+ evoked the concomitant release of dopamine beta-hydroxylase in a similar manner to the Ca2(+)-dependent secretion. The stimulation of catecholamine secretion by low concentrations of Ba2+ was markedly inhibited by protein kinase inhibitors, polymyxin B and trifluoperazine (TFP). The inhibitory action of polymyxin B, but not that of TFP, on the Ba2+ action was attenuated by elevating the concentration of Ba2+ in the incubation mixture. The stimulatory action of Ba2+ was enhanced by a protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA). In contrast to the acute effect of TPA, chronic exposure of chromaffin cells to high concentration of TPA reduced catecholamine secretion stimulated by Ba2+ as well as high K+ and carbamylcholine. These findings suggest the possibility that Ba2+ may activate Ca2(+)-mediated secretory processes presumably through its action on protein kinase C, thus resulting in the stimulation of catecholamine secretion from bovine adrenal chromaffin cells.
Hamano
S
S
Department of Pharmacology, Tokushima University School of Medicine, Japan.
Morita
K
K
Azuma
M
M
Oka
M
M
Teraoka
K
K
D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002395:Catecholamines; D047428:Protein Kinase Inhibitors; D001464:Barium; D004299:Dopamine beta-Hydroxylase; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium