Regulations by cyclic nucleotides and phorbol ester of calcium efflux from cultured bovine adrenal chromaffin cells.
The effects of cyclic nucleotides and phorbol ester on Ca2+ efflux from cultured bovine adrenal chromaffin cells were examined. Dibutyryl cyclic AMP (DB-cAMP), forskolin (an activator of adenylate cyclase), dibutyryl cyclic GMP (DB-cGMP) and nitroprusside (an activator of guanylate cyclase) all stimulated 45Ca2+ efflux from the cells preloaded with 45Ca2+. These agents did not increase the intracellular free Ca2+ ([Ca2+]i) level. On the contrary, phorbol 12-myristate 13-acetate (PMA; an activator of protein kinase C) did not affect the efflux of 45Ca2+, but inhibited the increase in 45Ca2+ efflux caused by DB-cAMP, forskolin, DB-cGMP or nitroprusside. The 45Ca2+ effluxes stimulated by cyclic nucleotides, forskolin and nitroprusside were inhibited by deprivation of extracellular Na+ ([Na+]o). These results suggest that both cAMP- and cGMP-dependent protein kinases are involved in the stimulatory mechanism of [Na+]o dependent Ca2+ efflux, probably through acceleration of [Na+]o/[Ca2+]i exchange and that protein kinase C plays an inhibitory role in this mechanism.
Houchi
H
H
Department of Pharmacology, School of Medicine, University of Tokushima, Japan.
Okuno
M
M
Shono
M
M
Tokumura
A
A
Oka
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured / Q000187:drug effects; D002838:Chromaffin System / Q000187:drug effects*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009712:Nucleotides, Cyclic / Q000494:pharmacology*; D010703:Phorbol Esters / Q000494:pharmacology*; D013997:Time Factors
D009712:Nucleotides, Cyclic; D010703:Phorbol Esters; D009599:Nitroprusside; D005576:Colforsin; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium