Polyphosphoinositide hydrolysis is associated with exocytosis in adrenal medullary cells

[3H]inositol-labelled products are released from adrenal medullary cells during exocytotic secretion. In 'leaky' cells in which small molecules readily enter and leave the cytoplasm, addition of micromolar calcium ions in the presence of ATP stimulates exocytosis and causes the release of inositol polyphosphates. These data support the idea that hydrolysis of plasma membrane polyphosphoinositides may be an essential step in exocytotic secretion.