Age-dependent losses in the penetrability of mouse eggs

Abstract

The fertilizable life of mammalian eggs retained in the oviduct is limited; in the mouse, estimates vary from 10–15 hr (for review, see Iwamatsu & Chang, 1971), but the effect of egg age on the kinetics of sperm penetration has not been examined thoroughly. In considering age-dependent losses in egg fertilizability, both in vivo and in vitro, we were interested in differentiating between changes occurring at the zonal level versus those affecting the sperm–egg fusion process, i.e. vitellus-related. Accordingly, sperm penetration of zona-intact and zona-free eggs was investigated.