HYPOPHYSECTOMY OF THE CYCLIC MOUSE .2. EFFECTS OF FOLLICLE-STIMULATING-HORMONE (FSH) AND LUTEINIZING-HORMONE ON FOLLICULOGENESIS, FSH AND HUMAN CHORIONIC-GONADOTROPIN RECEPTORS, AND STEROIDOGENESIS

This study was designed to determine the effects of FSH and LH on ovar ian follicular development in adult hypophysectomized (HX) mice. Twelv e days after HX, the animals received s.c. injections of ovine FSH (oF SH; 4 mug/day) or oFSH (4 mug/day) plus ovine LH (oLH; 2 mug/day) twic e a day for 1 to 4 days. After 4 days of treatment with FSH alone, the number of preantral follicles (stages 1-3) increased significantly co mpared to that in HX controls and reached cyclic numbers; however, inc orporation of [H-3]thymidine into these preantral follicles as compare d to HX controls did not increase. The number of healthy antral follic les (stages 4-5) and incorporation of [H-3]thymidine into stage 5 foll icles started to increase after only 1 day of treatment with FSH, and the number of atretic follicles concomitantly decreased. Treatment wit h both FSH and LH for 1 to 4 days increased the number of healthy foll icles and restored DNA synthesis at all stages ( 1-5) to normal levels . Two days of replacement with FSH or FSH plus LH was required for fol licles to attain preovulatory size (stage 6). FSH alone induced FSH an d hCG receptors in granulosa cells, but without the induction of theca l LH /hCG receptors; FSH induced production of progesterone and andros tenedione by stage 6 follicles, but not estradiol (E2) accumulation in the incubation medium or in the serum. Combined FSH and LH induced hC G receptors in the theca and interstitium, and also restored follicula r E2 production to proestrous values. LH alone increased only the numb er of stage 2-3 follicles. Unexpectedly, LH alone also induced thecal hCG receptors as well as FSH receptors in granulosa cells of preantral and antral follicles. The present results demonstrate that FSH is ess ential for follicular growth at all stages and for prevention of atret ic antral follicles. Both FSH and LH are necessary for regulation of f ollicular development and differentiation from the earliest preantral to preovulatory stages.