Evidence for a binding site on the sperm plasma membrane which recognizes the murine zona pellucida: A binding site on the sperm plasma membrane

Murine cauda epididymal sperm preincubated in either a modified Krebs-Ringer or M 199 solution bind to cumulus-free, zona pellucida-intact eggs. Pretreatment of such eggs with an affinity purified preparation of the seminal inhibitor binding component (acceptor), isolated from epididymal sperm, reduces in a concentration dependent manner, the number of sperm that bind. Treatment of cauda sperm, preincubated in either of the above two media, with the seminal inhibitor, also reduces the number of sperm able to bind. Incubation of cauda sperm in the Krebs-Ringer solution for up to 4 h does not affect their ability to bind the seminal inhibitor. Omission of bovine serum albumin from the preincubation medium results in a significant reduction in sperm binding. These data are interpreted to mean that the seminal inhibitor acceptor sites on the sperm surface of incubated sperm function in the in vitro binding to the zona pellucida.