ATP-induced release of vasopressin from isolated bovine neurohypophyseal secretory granules. Dependency on chloride and effects of analogues of ATP.

Secretory granules isolated from bovine neurohypophyses released vasopressin in the presence of a buffered medium containing ATP, Mg2+ and KCl. Substitution of K+ in the medium with Na+ or choline did not affect the release. Substitution of Cl- with either sucrose, sulphate or acetate strongly reduced the release. Analogues of ATP, substituted at the beta-gamma anhydride bond with methylene or imido groups caused a smaller release which was not related to a very small breakdown of analogues that occurred. It is suggested that at least part of the ATP induced release is due to a physicochemical action.