Absence of a Ca response following ammonia activation of sea urchin eggs

Following insemination of sea urchin eggs, both the rate of Ca uptake by the eggs and the rate of Ca efflux from the eggs increase (see text for references). We find that both of these components of the egg's Ca response are absent following partial activation with ammonia. This suggests that the so-called “late events” of fertilization, which are activated by ammonia treatment, are not mediated directly by changes in egg Ca.