Exocytotic release of catecholamine from perfused adrenal gland of guinea-pig induced by veratridine.

1 Experiments were carried out on perfused adrenal glands of guinea-pig to determine whether veratridine caused the exocytotic release of catecholamine by comparing its effect with that of splanchnic nerve stimulation and secretagogues such as acetylcholine and excess K+. 2 Veratridine (100 microM) and excess K+ (56 mM) caused secretion of catecholamine and dopamine-beta-hydroxylase (DBH) activity in the venous effluents in the presence of atropine (30 microM) and hexamethonium (2 mM). Splanchnic nerve stimulation in the presence or absence of physostigmine (100 nM) and infusion of acetylcholine in the presence of physostigmine had the same effect. In all the responses, the release of DBH tended to last for a longer period than that of catecholamine. 3 The ratio of catecholamine to DBH activity appearing in the venous effluents was approximately 9, regardless of the method of stimulation. This value was close to the ratio of catecholamines to the 'soluble' DBH activity found in the chromaffin granules. 4 All the types of stimulation used caused a proportional release of adenine nucleotides and catecholamines in the effluents. The adenine nucleotides were mainly adenosine 5'-phosphate. 5 The ratio of catecholamine to adenine nucleotides was approximately 11, regardless of the method of stimulation. 6 It is suggested that the release of catecholamine induced by veratridine occurs by exocytosis in adrenal glands of guinea-pig.