title: Distinct regulations by calcium of cyclic GMP levels and catecholamine secretion in isolated bovine adrenal chromaffin cells.
abstract: The effects of various calcium-dependent secretagogues on cyclic GMP levels and catecholamine (CA) secretion were measured in a preparation of bovine adrenal chromaffin cells. The secretory effect of acetylcholine (ACh; 8--10 fold stimulation) was mimicked by nicotine but not muscarine. Three--five fold stimulations of cyclic GMP levels were also obtained with ACh and muscarine but not nicotine. High concentration of K+, and the ionophore A23187, also elevated cyclic GMP levels. However, secretion produced by veratridine, ouabain, and the ionophore X537A was not accompanied by any rise in cyclic GMP levels. Removal of extracellular calcium significantly decreased both basal levels of CA secretion and of cyclic GMP and completely abolished their stimulation by ACh. The half-maximal effects of calcium on the cholinergic stimulations of cyclic GMP levels and of CA secretion were observed at 0.2 and 2.5 mM, respectively. Substitution of Ca2+ by Sr2+ was more effective in maintaining the cyclic GMP response than the secretory response. The calcium channel blockers Co2+, Mg2+ and Ni2+ inhibited the cholinergic stimulation of cyclic GMP more than that of CA release. On the other hand, the organic calcium channel blockers, verapamil and methoxyverapamil (D--600) were more effective antagonists of the secretory response. These data indicate that the cholinergic stimulations of CA secretion and of cyclic GMP levels in bovine adrenal chromaffin cells are regulated by calcium via two distinct mechanisms.
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002417:Cattle; D002838:Chromaffin System / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007476:Ionophores / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D010277:Parasympathomimetics / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D007476:Ionophores; D010277:Parasympathomimetics; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine