Abstract
Embryo recovery and subsequent embryonic development from guinea pigs treated with or without Inhibin vaccines were compared to determine the effect of active immunization against the inhibin α-subunit. Twenty female guinea pigs of the Hartley strain were injected 3 times either with 1ml inhibin vaccine (recombinant ovine inhibin α-subunit in oil emulsion: 50μg/ml, inhibin-immunized group), or 1ml placebo (saline in oil emulsion; control group) at 4 week intervals. After one estrous cycle following the last injection, females were naturally mated and embryos were collected at 11:00hr of day 6 of pregnancy (Day 1: sperm in the vaginal smear) for culture in vitro. Active immunization increased the number of corpora lutea (12.6±3.0 vs. 4.6±0.2, P<0.05), recovered embryos (9.8±1.9 vs. 3.6±0.4, P<0.01) and normal embryos (7.8±1.4 vs. 3.6±0.4, P<0.05), although estrous cycle length was not affected (P>0.05). During subsequent 8 day culture in vitro, most of the recovered embryos formed trophoblast outgrowth; 100% (14/14) and 88.2% (15/17) in control and immunized groups, respectively. High levels of inhibin antibody titers were sustained in the Inhibin-immunized guinea pigs at least for 5 months after the last injection while no antibody titer was detected in the control animals. These results indicate that active immunization against the inhibin α-subunit is a long-acting and efficient method to induce superovulation with normal embryonic development in the guinea pig.
