Alteration of Sites on the Mammalian Sperm Surface following Capacitation

THE ovum cannot be penetrated by a spermatozoon until the latter undergoes a change termed capacitation 1 which, in the golden hamster, can be produced in vitro by incubation in various,body fluids 2–4 including serum 5 and (β-glucuronidase 6 . The process involves vesiculation of the plasma membrane with the outer acrosomal membrane 7 , which in turn seems to release egg-penetrating enzymes and exposes a surface which can fuse with the vitelline membrane of the egg 8 . As part of a series of investigations on the nature of these surface changes we have studied the effect of proteolytic enzymes on the adherence of sperm to eggs in vitro . Our results show that adherence of sperm to the zona pellucida is species specific both before and after capacitation. Capacitation alters the sperm surface, however, so that it will no longer adhere to trypsin-treated eggs.