Superovulation, fertilization and in vitro embryo development in mice after administration of an inhibin-neutralizing antiserum.

The present study was conducted to investigate the effect of immunoneutralization against endogenous inhibin on oocyte and embryo production in adult and immature mice. At 12:00 h on day 2 of oestrus (day 1 of dioestrus), a single i.p. injection of inhibin antiserum (50, 100, 200 or 400 microl per animal) or equine chorionic gonadotrophin (eCG; 10 or 20 iu per animal) or control goat serum (100 microl per animal) was administered to adult female mice. After 48 h, the mice in each of the three groups were given a single i.p. injection of hCG (10 iu per animal). At 42 h after hCG injection, ova were collected from oviducts and cultured in KSOM solution. Treatments with both inhibin antiserum-hCG and eCG-hCG induced superovulation in all the animals tested. The number of oocytes in animals treated with inhibin antiserum was significantly higher (P < 0.05) compared with the control group, and the number of oocytes ovulated in animals treated with 200 or 400 ml inhibin antiserum was significantly (P < 0.05) higher than that in animals treated with 10 or 20 iu eCG. The superovulated oocytes that were fertilized normally in vivo were able to form blastocysts in vitro. The rate of blastocyst development for animals treated with 50-200 ml inhibin antiserum was significantly (P < 0.05) higher than that of the eCG-treated animals. Irrespective of the day of the oestrous cycle, 200 microl inhibin antiserum administered at 12:00 h on each of 4 days induced superovulation in all the animals tested. The rates of oocyte and embryo production by these animals were significantly (P < 0.05) higher than in the control groups. Furthermore, administration of inhibin antiserum at doses of 50, 100, 200 or 400 ml produced similar results in 26-day-old immature mice. These results indicate that passive immunoneutralization of endogenous inhibin alpha-subunit induces superovulation in immature and adult mice. The superovulated oocytes obtained by administration of inhibin antiserum have normal embryonic developmental competence. Thus, it is concluded that this inhibin antiserum method is a new practical alternative for induction of superovulation in mice instead of the more commonly used eCG-hCG protocol.