Na(+)-dependent Ca2+ efflux inhibits stimulus-induced secretion in bovine chromaffin cells.
Stimulations of chromaffin cells with histamine and ionomycin produced rises in cellular free Ca2+ level. The removal of Na+ ions from the medium prolongated the rises without changing the magnitude. The stimulations also facilitated 45Ca2+ efflux from cells by over 3-fold. The facilitation was, however, largely abolished by the Na+ removal, indicating the Na(+)-dependent efflux is a major system to expel Ca2+ from the stimulated cells. The Na+ removal also enhanced secretions evoked by these stimuli. The results suggest the Na(+)-dependent Ca2+ efflux by lowering the elevated cellular Ca2+ plays a role in terminating the stimulus-induced secretion.
Goh
Y
Y
Shionogi Research Laboratories, Shionogi & Co., Ltd, Osaka, Japan.
Kurosawa
A
A
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D005456:Fluorescent Dyes; D016257:Fura-2; D006632:Histamine / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*
D001572:Benzofurans; D002395:Catecholamines; D005456:Fluorescent Dyes; D015759:Ionomycin; D006632:Histamine; D012964:Sodium; D002118:Calcium; D016257:Fura-2