Induction of superovulation by inhibin vaccine in cyclic guinea-pigs

Experiments were conducted to determine whether neutralizing endogenous inh ibin affects follicular development and ovulation rate in guinea-pigs. Eigh teen female guinea-pigs bearing 4 week progesterone implants were divided i nto three groups. At 1 week after removal of the progesterone implants, the animals were given a s.c. injection of 1 mi placebo (saline in oil emulsio n; control), or 25 or 50 mu g inhibin vaccine three times at 4 week interva ls. Blood samples were collected once a week throughout the experiment for measuring inhibin antibody titres. After the third injection of inhibin vac cine, blood samples and ovaries were collected on the morning of day 8 afte r the day of oestrus. Inhibin vaccine increased the ovulation rate in a dos e-dependent manner (placebo: 4.2 +/- 0.4; 25 mu g inhibin vaccine: 6.2 +/- 0.9; 50 mu g inhibin vaccine: 9.8 +/- 0.9) without any effects on the durat ion of the oestrous cycle. The results also showed that active immunization against inhibin increased the number of atretic follicles of 300-399 mu m in diameter on day 8 after ovulation. The present study is the first to sho w that the active immunization against inhibin may be a useful method for i nducing multiple ovulation in guinea-pigs.