Effect of pregnant mare's serum gonadotropin on increased ovulation in guinea pigs with synchronized estrous cycle

An ability of Pregnant Mare's Serum Gonadotropin (PMSG) to induce superovulation was investigated in guinea pigs with synchronized estrous cycle caused by the treatment for 21 days of progesterone tubing. On day 6 later following the removal of progesterone treatment, every animal given saline injection had synchronously ovulated. When compared with saline control, a significant increase of ova ovulated was induced by an injection of PMSG 8 hours before the removal of progesterone tubing, but not by the other PMSG treatment schedule. Present study indicates that PMSG injection given at a fixed stage of synchronized estrous cycle induced superovulation in guinea pigs treated with long-term implantation of progesterone tubing.