Effect of cAMP-dependent protein kinase on catecholamine secretion from bovine adrenal chromaffin cells.
We examined the role of cAMP-dependent protein kinase in Ca(2+)-elicited catecholamine secretion from bovine adrenal chromaffin cells. When the digitonin-treated cells were incubated with the catalytic subunit of cAMP-dependent protein kinase, the secretion of catecholamines from the cells occurred in the absence of Ca2+. The effect of the catalytic subunit was dependent on its activity (50-100 units/ml) and the presence of ATP-Mg2+ in the incubation medium. However, incubation of the cells with the regulatory subunit of cAMP-dependent protein kinase did not affect the secretion. Ca2+ (43 nM-10 microM) also increased the secretion, which was ATP-Mg(2+)-dependent. The catalytic subunit (25-200 units/ml) enhanced the Ca(2+)-evoked secretion at the suboptimal but not optimal Ca2+ concentration, which induced maximal secretion. A potent synthetic peptide inhibitor of cAMP-dependent protein kinase abolished the catalytic subunit-induced secretion, but not the Ca(2+)-evoked secretion. On the other hand, K-252a, a potent inhibitor of protein kinases, inhibited both the catalytic subunit-induced and the Ca(2+)-evoked secretion, but not KT5823, a much less potent inhibitor of protein kinases. These results strongly suggest that the catalytic subunit of cAMP-dependent protein kinase produces the secretion of catecholamines via protein phosphorylation. The results further suggest that the cAMP-dependent protein kinase does not participate in an intrinsic process of Ca(2+)-elicited secretion but it may act as a modulator.
Tachikawa
E
E
Department of Pharmacology, School of Medicine, Iwate Medical University, Morioka, Japan.
Furumachi
K
K
Yanagihara
N
N
Kashimoto
T
T
Takahashi
S
S
Izumi
F
F
D000302:Adrenal Cortex / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D026121:Indole Alkaloids; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D002227:Carbazoles; D002395:Catecholamines; D026121:Indole Alkaloids; D004533:Egtazic Acid; C049985:staurosporine aglycone; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium