Oocyte normality after superovulation in immature rats.

The developmental ability of oocytes recovered from superovulated immature rats (40 i.u. PMSG) was compared with that of oocytes from control rats (4 i.u. PMSG). Oocytes were collected from the oviducts immediately after ovulation or from large follicles, and were transferred to one ovarian bursa of normal adult recipients. Fertilization and subsequent fetal development occurred in the recipients which were killed on Day 20. The proportions of oocytes surviving after transfer from the oviducts of donors which received 4 or 40 i.u. PMSG or from the follicles of those which received 40 i.u. PMSG were not significantly different. However, the proportion of oocytes surviving after recovery from the follicles of donors receiving 4 i.u. PMSG was significantly higher (P less than 0.05). These studies suggest that oocytes recovered from superovulated or control rats are equally able to develop, and the failure to maintain pregnancy that has been reported for superovulated rats in previous studies is not attributable to defects in the oocytes.