Effects of nitroprusside and nicorandil on catecholamine secretion and calcium mobilization in cultured bovine adrenal chromaffin cells.
The effects of nitroprusside and nicorandil on catecholamine secretion and free intracellular Ca2+ ([Ca2+]i) mobilization in bovine adrenal chromaffin cells were studied to evaluate the role of the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway in the regulation of a [Ca2+]i-dependent secretory process. These effects were compared with those of nifedipine, a typical voltage-dependent Ca2+ channel blocker. Carbachol produced a rapid increase followed by a sustained increase of [Ca2+]i (Ca2+ transient) in cultured bovine adrenal chromaffin cells. Both nitroprusside and nicorandil accelerated the decrease in [Ca2+]i without changing the peak values of the initial [Ca2+]i increase of Ca2+ transient. These drugs, however, did not affect carbachol-induced catecholamine secretion, suggesting that secretion is related to the initial [Ca2+]i increase and not to a late sustained [Ca2+]i increases. However, nifedipine reduced the peak and duration of carbachol-induced [Ca2+]i increases and decreased the secretion of catecholamines. Diethylamine/NO complex, an NO donor, and dibutyryl-cGMP produced similar changes in Ca2+ transient and did not alter catecholamine secretion, suggesting that the effects of nitroprusside and nicorandil were mediated by the NO/cGMP pathway. These results indicated that the pattern of Ca2+ transient, especially the initial increase in [Ca2+]i, is important in secretion of catecholamine.
Shono
M
M
General Laboratory for Medical Research, Tokushima University School of Medicine, Japan.
Houchi
H
H
Oka
M
M
Nakaya
Y
Y
D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism; D005905:Glyburide / Q000494:pharmacology; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D020108:Nicorandil; D009543:Nifedipine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D002395:Catecholamines; D014665:Vasodilator Agents; D009599:Nitroprusside; D009536:Niacinamide; D020108:Nicorandil; D009543:Nifedipine; D005905:Glyburide; D002118:Calcium