Induction of zonal and egg plasma membrane blocks to sperm penetration in mouse eggs with cortical granule exudate.

Abstract

The contents of cortical granules (cortical granule exudate = CGE) were recovered from zona-free mouse eggs inseminated in vitro with capacitated epididymal spermatozoa. Preincubation of cumulus-free, zona-intact eggs in CGE led to reduced penetration levels upon insemination. This reduction was CGE concentration- and time-dependent and was susceptible to inhibition by soybean trypsin inhibitor and by p-aminobenzamidine. Control experiments eliminated active contributions from the sperm suspension used to elicit granule release. CGE was also active in reducing penetration of zona-free eggs. These results indicate that cortical granule contents are capable of modulating sperm penetration of mouse eggs at both the zona pellucida and at the egg plasma membrane.