Pure FSH alone induces ovulation and subsequent pregnancy in the mouse resulting in fetal development.

The role of FSH in inducing folliculogenesis is well established. Recently, the availability of pure FSH has led to a reevaluation of its role in the process of ovulation. Previously, these functions have been examined separately, usually with pregnant mares' serum gonadotropin (PMSG) followed by FSH for ovulation or FSH for folliculogenesis followed by hCG for ovulation. To determine if FSH alone can induce both folliculogenesis, ovulation and establish a functioning corpus luteum without exogenous LH, we injected sexually mature intact mice (CD-1) with either ovine FSH (oFSH, 5 micrograms; < 0.2% LH contamination) or recombinant FSH (RCFSH, 1 IU; devoid of any LH activity) to stimulate folliculogenesis, followed forty-eight hours later by a second injection of the same preparation (oFSH, 15 micrograms; RCFSH, 1 IU, respectively) to induce ovulation. Injected female mice were mated individually with a fertile male. On days 15-17, pregnancy rates and fetal development were obtained for each animal and were compared with controls, mice injected with PMSG (1 IU) followed by hCG (1 IU). oFSH/oFSH and RCFSH/RCFSH results were combined since no statistical significant differences were detected between these groups. The pregnancy rate for the group receiving FSH/FSH (78.3%, n = 23) was higher than that of the PMSG/hCG group (48.3%, n = 27; p = .02). The number of fetuses produced per mouse in animals receiving FSH alone (8.5 +/- 1.1; mean +/- S.E.) also was greater than the controls (4.5 +/- 99; p = .01). We conclude that the ability of these animals to proceed beyond ovulation to implantation with fetal development demonstrates FSH's ability to cause not only follicular maturation and rupture, but also granulosa cell luteinization, further identifying the potentially important role of FSH in the ovulatory process.