Progesterone and estradiol regulate sperm hyperactivation and in vitro fertilization success in mice.

Progesterone (P) and 17ß-estradiol (Eß) form the well-known hormone pair that regulates sperm capacitation. Here, we examined the regulatory effects of P and Eß on sperm hyperactivation in mice and evaluated the in vitro fertilization (IVF) success. Although P enhanced hyperactivation, Eß dose-dependently suppressed the P-enhanced hyperactivation. Moreover, P increased IVF success, whereas Eß suppressed the P-induced increase in IVF success in a dose-dependent manner. Thus, P and Eß competitively regulate hyperactivation and IVF success in mice. Since P and Eß concentrations generally change during the estrous cycle, sperm are speculated to capacitate in response to the oviductal environment and fertilize the oocyte.