Sperm-egg interaction in the mouse using live and glutaraldehyde-fixed eggs.

A study of interaction between gametes in the mouse, using live and glutaraldehyde-fixed eggs, showed that, while in live eggs the binding is a two-step process ("early" and "late" binding), the process is one step when the spermatozoa interact with fixed eggs. The second point that emerged from this study is that uncapacitated and capacitated spermatozoa bind the zonae pellucidae of live and fixed eggs in the same way, but only the capacitated spermatozoa bound to live eggs undergo a complete acrosome reaction and penetrate the zona pellucida. Moreover, it has been shown that binding to fixed eggs, just as to live eggs, is Ca2+-dependent, and it can be reversed by EGTA. Fixed eggs thus are a good model to study only one step of the sperm-egg interaction removed from all the other events of the fertilization process.