SPERM BINDING TO THE MOUSE EGG PLASMALEMMA

The sperm binding properties of the mouse egg plasmalemma wre assessed following an in vitro challenge of zona-free eggs with capacitated epididymal sperm. Unpenetrated eggs were capable of binding more sperm than were their in vivo or in vitro penetrated counterparts over a wide range in sperm concentration. Only capacitated sperm bound and binding was physiologic because it culminated in penetration of the vitellus. Kinetic analysis of these phenomena indicated that sperm detached after the egg was penetrated and it is suggested that this is a cause and effect relationship reflecting early aspects of the block to polyspermy response.