Fertilization increases the polyphosphoinositide content of sea urchin eggs

Fertilization of the sea urchin egg stimulates a wave of exocytosis of cortical vesicles, but the mechanism by which fertilization regulates this secretion is not fully understood. We describe here experiments which suggest that polyphosphoinositide metabolism could be a factor in this regulation. We find that the cortical vesicle exocytosis in the egg of Strongylocentrotus purpuratus is preceded by a 40% increase in its content of triphosphoinositide (TPI) and a 22% increase of diphosphoinositide (DPI).