Uptake OF Ca2+ is one of the earliest responses to fertilization of sea urchin eggs

Abstract

Sea urchin eggs take up Ca for 10 min following insemination (determined as uptake of ⁴⁵Ca from the SW (3)). Although 90% of this uptake occurs after the beginning of the cortical reaction and may represent external binding of Ca to the egg surface coats, there is a brief phase of uptake (0–30 sec) which precedes the cortical reaction; this may represent a Ca flux into the eggs.