Development of embryos in superovulated guinea pigs following active immunization against the inhibin alpha-subunit

Embryo recovery and subsequent embryonic development from guinea pigs treat ed with or without inhibin vaccines were compared to determine the effect o f active immunization against the inhibin a-subunit. Twenty female guinea p igs of the Hartley strain were injected 3 times either with 1 mi inhibin va ccine (recombinant ovine inhibin a-subunit in oil emulsion: 50 mu g/ml, inh ibin-immunized group), or 1 mi placebo (saline in oil emulsion; control gro up) at 4 week intervals. After one estrous cycle following the last injecti on, females were naturally mated and embryos were collected at 11:00 hr 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 g uinea gigs at least for 5 months after the last injection while no antibody titer was detected in the control animals. These results indicate that act ive immunization against the inhibin cu-subunit is a long-acting and effici ent method to induce superovulation with normal embryonic development in th e guinea pig.