PHYSIOLOGICAL MECHANISM OF EGG ACTIVATION

In all species, eggs are activated at fertilization by an increase in intracellular free Ca2+. In frogs, fishes and echinoderms the increase in cytoplasmic free calcium fakes the form of a single explosive wave while, in mammals the spermatozoon triggers a series of calcium oscil lation that last for several hours, A major unresolved is determinatio n of the mechanism that the spermatozoon uses to trigger this calcium increase in the egg at fertilization. This review will recall the vari ous hypothesis on the signal transduction system and present the recen t argument for a soluble sperm cytosolic factor.