Fertilization-Associated Changes in the Murine Zona Pellucida: A Time Sequence Study

Abstract

The temporal sequences in fertilization-associated changes in mouse zonae pellucidae were defined. Zonae solubility in mercaptoethanol began to change as early as one hour postinsemination in vitro, at approximately the time sperm-egg fusion was first seen, and required at least one additional hour to reach completion. Striking differences were apparent in the sperm binding properties of zonae of unfertilized ova and those of in vivo produced 2-cell embryos. Zonae of embryos recovered 2-7 h after the anticipated time of sperm penetration behaved like those of unfertilized eggs. Only zonae of 10 h embryos displayed sperm binding properties comparable to the 2-cell embryo. However, modification of the sperm binding assay procedure led to the demonstration of less dramatic zonae changes which occurred within 2 h of sperm penetration.