Ovulation in the tree shrew (Tupaia belangeri) induced by gonadotrophins

The induction of ovulation by exogenous gonadotrophins is an important approach for recovering oocytes used for studies on the reproductive biology of some mammals. In the present study, pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) were used to induce ovulation in the tree shrew (Tupaia belangeri) using the following regimens. Groups A1-A3, multiple injections of PMSG (30-60 IU) followed by a single dose of hCG (30-60 IU); B1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (60 IU); E1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (30 IU) plus PMSG (30 IU); and administration of either PMSG (C1 and C2) or hCG (D1). The ovulation rate of animals producing oocytes with either first polar body or distinct perivitelline space, and the mean number of oocytes per animal were considered the most important criteria in each regimen. The most effective induction of ovulation was achieved in groups B1 and E1, with ovulation rates of 4/4 and 4/4, respectively, and mean numbers of ovulated oocytes per animal of 3.25 +/- 0.48 and 4.00 +/- 0.71 respectively. No ovulation was observed in the control group or in group D1. Therefore, regimes B1 and E1 were considered as the simplest and most effective for the induction of ovulation in the tree shrew.