The different effects of D-600 (methoxyverapamil) on the release of adrenal catecholamines induced by acetylcholine, high potassium or sodium deprivation.

1 Bovine adrenal glands were perfused with Locke solution and catecholamine release was induced by acetylcholine, by a depolarizing concentration of potassium, or by omission of sodium from the perfusion fluid. 2 D-600 (methoxyverapamil) at the concentration of 30 muM produced a 23% inhibition of catecholamine release evoked by acetylcholine (0.1 mM) in the presence of physostigmine (10 muM). 3 A concentration of D-600 of 0.3 mM produced 86% and 85% inhibition in the output of catecholamines in response to acetylcholine and high potassium respectively. 4 D-600 (0.3 mM) failed to block the release of catecholamines evoked by sodium deprivation. 5 The results suggest the involvement of intracellular calcium in the exocytotic release of catecholamines induced by sodium omission.