Inhibition of Sperm Capacitation in vitro by Contraceptive Steroids

Abstract

THE way in which small doses of progesterone prevent fertility without inhibiting ovulation is unknown. Inhibition of uterine decidualization may be involved, or increased viscosity of cervical mucus. A third possibility is that these contraceptive steroids interfere with capacitation, a process by which sperm undergo a final maturation enabling them to fertilize ova¹. Capacitation has been demonstrated in several species² and there is some evidence that it occurs in humans^3,4. The process seems to be horrnonally regulated, for in rabbits it depends on the level of gonadotrophin⁵, does not occur in the pseudopregnant animal⁶ and is reduced by injections of progesterone⁷. Hamster sperm can be capacitated in vitro with follicular fluid or the contents of an oviduct^8,9, and these techniques made it possible for us to determine the effects of contraceptive steroids on the Capacitation process.