Induction of Zonal and Egg Plasma Membrane Blocks to Sperm Penetration in Mouse Eggs with Cortical Granule Exudate

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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.