ATP-induced release of vasopressin associated with phosphorylation of isolated bovine neurohypophyseal secretory granule membranes.

Secretory granules isolated from ox neurohypophyses released their content of vasopressin in the presence of ATP and Mg2+. A half maximal ATP concentration of 0.25 mM was found. Ca2+ was not necessary for the effect. High concentrations of ADP, AMP and ITP were shown to mimic the effect of ATP. Utilizing this effect of ATP combined with iodonitrotetrazolium treatment to make mitochondria heavier, a method is described to obtain granule "ghosts" in a purified form. They were shown to be phosphorylated when granules were incubated with [gamma-32P] ATP.