Fertilization of Pronase-Treated Mouse Ova in Vitro

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Abstract
To obtain consistently a large number of zona-free mouse ova for studies of sperm-egg interactions, a study was made of the relative effectiveness of removing the zona pellucida from ova by mechanical or enzymatic treatments. Ova exposed to pronase [PN] before mechanical removal of the zona pellucida in medium devoid of PN had similar fertilization rates in vitro compared with ova mechanically denuded in the absence of PN. Ova with PN-weakened zonae were easier to denude and survived the mechanical manipulations better than the ova denuded by vigorous aspiration in narrow-bore pipettes. PN exposure significantly lowered the incidence of polyspermy in the naked ova; some enzyme may have diffused across the perivitelline space and damaged sperm-binding sites on the vitelline plasma membrane. The enzyme treatment also reduced the zona-intact ova fertilization rate.