Capacitation is defined herein as a set of changes in the sperm plasma membrane that enables sperm to undergo the acrosome reaction. Hyperactivation is an increase in flagellar beat amplitude and asymmetry that is observed in sperm recovered from the ampulla of the oviduct near the time of ovulation. Capacitation of bull sperm is enhanced by incubation in medium conditioned by oviductal epithelium or in oviduct fluid. Hyperactivation of human sperm may be enhanced by incubations with cultured oviductal epithelium. Knowledge of how the oviductal reservoir modulates sperm transport and capacitation could be applied to increasing the reproductive efficiency of cattle and other valuable species. asthma inhalers
There is strong evidence from multiple species that the oviductal reservoir is created by binding of sperm to oviductal epithelium. Motile sperm have been observed to bind to the apical surface of the oviductal epithelium in cattle (Fig. 1), mice, hamsters, pigs, and horses. The trapping action of the sperm-binding moieties may be enhanced by the narrow lumen of the uterotubal junction and isthmus. The bovine lumen is particularly tortuous and narrow in the uterotubal junction.
FIG. 1. A) Bull sperm binding to explants of bovine oviductal epithelium in vitro (differential interference contrast optics, X700; protocol described in ). B) Scanning electron micrograph of bull sperm attached to bovine oviductal epithelium after infusion in vivo (XI700; adapted from Lefebvre etal., Biol Reprod 1995; 53:1071, Figure 4C ).