| Abstract: | When cultured bovine adrenal chromaffin cells were stimulated by a nicotinic agonist, carbamylcholine (0.3 mM) or 1,1-dimethyl-4-phenylpiperazinium (50 microM), in the Ca2+-free medium containing 0.1 mM ethyleneglycoltetraacetic acid, intracellular free Ca2+ concentration (Ca2+]i) rose from approximately 90 to 149 nM. High K+ (56 mM) and veratridine (50 microM) had no effect on the Ca2+]i in Ca2+-free medium. The carbamylcholine-evoked rise in Ca2+]i was blocked by hexamethonium (0.1 mM) but not by atropine (1 microM). Furthermore, the carbamylcholine-evoked rise in Ca2+]i was inhibited by an intracellular Ca2+ antagonist, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxy-benzoate hydrochloride (10 microM) but not by a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (20 microM). These results show the existence of intracellular Ca2+ store sites, from which Ca2+ is released upon nicotinic receptor stimulation, in cultured adrenal chromaffin cells. |
