Vol. 129, No. 2, 1985 BlOCHEMlCALANDBlOPHYSlCALRESEARCHCOMMUNlCATlONS June 14,1985 Pages 511-516 THE PHORBOL ESTER TPA ENHANCES A23187- BUT NOT CARBACHOL- AND HIGH K+-INDUCED CATECHOLAMINE SECRETION FROM CULTURED BOVINE ADRENAL CHROMAFFIN CELLS Kyoji Morita, Keith W. Brocklehurst, Stuart M. Tomares, and Harvey 8. Pollard L'aboratory of Cell Biology and Genetics, National Institute of Arthritis, Diabetes, and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland 20205 Received May 6, 1985 SUMMARY: The effect of the phorbol ester TPA on catecholamine secretion was studied in cultured bovine adrenal chromaffin cells. The pretreatment of chromaffin cells with TPA caused the enhancement of catecholamine secretion induced by the calcium ionophore, A23187. By contrast, neither carbachol- nor high K+-induced secretion was changed by TPA pretreatment. These results support the concept that protein kinase C plays an important role as a factor transducing the Ca2+ signal to the exocytotic process of catechol- amine secretion in bovine adrenal chromaffin cells. B 1985 Academic Press, Inc. Catecholamine secretion is a Ca2+ -aependent process which is initiated by a rise in the intracellular concentration of free Ca2+ ions [1,2]. However,, the details of this secretory process, particularly the mechanisms of Ca2+ action, remain poorly understood. One Ca2+ -sensitive enzyme possibly involved in the regulation of catecholamine secretion from chromaffin cells is the Ca 2+ -activated phospholipid-aependent protein kinase I(protein kinase C) which appears to play an important role in the release reaction of platelets [3]. The phorbol ester TPA activates protein kinase C by increasing its affinity for Ca2+ [4], and it has been shown that the cellular TPA receptor in brain copurified with protein kinase C 153. TPA causes an increase in the affinity of the exocytotic process for Ca 2+ in isolated chromaffin cells which have been permeabilized by electric discharge [6]. Abbreviations: TPA (12-0-tetradecanoylphorbol-13-acetate), -N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid), DMSO (dimethylsulfoxide) 0006-291X185 $1.50 511 Copyright 0 1985 by Academic Press, Inc. All rights of reproduction in any form reserved.