Potentiation by ouabain of catecholamine secretion from bovine adrenal chromaffin cells in culture induced by pituitary adenylate cyclase-activating polypeptide: evidence for involvements of Na+ and Ca2+ movements.
The effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on catecholamine secretion with ouabain, an inhibitor of Na(+)-K+ ATPase, in cultured bovine adrenal chromaffin cells was examined, to determine whether movement of Na+, as well as Ca2+, is involved in the secretory process. PACAP (10(-10)-10(-6)M)-induced catecholamine secretion was markedly potentiated by addition of ouabain (10(-5)M). When cultured cells were preincubated with PACAP for 30 min in Ca(2+)-free medium in the presence of ouabain and then stimulated for 15 min with Ca(2+)-containing medium without PACAP or ouabain, their catecholamine secretion was dependent on the external Ca2+ concentration, and 45Ca2+ influx into the cells was increased. When the cells had been preincubated with PACAP and ouabain in Na(+)-free sucrose medium, their Ca(2+)-induced catecholamine secretion was greatly reduced. PACAP increased 22Na+ influx into cells treated with ouabain. These results suggest that stimulation by PACAP and inhibition of the Na(+)-pump both increase the intracellular Na+ level, resulting in increase in Ca2+ influx and catecholamine secretion.
Azuma
M
M
Department of Pharmacy, University Hospital, School of Medicine, University of Tokushima, Japan.
Houchi
H
H
Minakuchi
K
K
Oka
M
M
Takasugi
M
M
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000502:physiology; D004357:Drug Synergism; D017136:Ion Transport; D009479:Neuropeptides / Q000008:administration & dosage*; D010042:Ouabain / Q000008:administration & dosage*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012964:Sodium / Q000378:metabolism
D002395:Catecholamines; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010042:Ouabain; D012964:Sodium; D000262:Adenylyl Cyclases; D002118:Calcium