Is there a role for estrogen in follicular maturation in the primate?

The present study focusses attention on the effects of blocking estrogen synthesis, during follicular phase, on follicular maturation in the adult female bonnet monkey (Macaca radiata). Administration of cycling females (n=4) with an aromatase inhibitor CGS 16949A (Al) by Alzet mini-pump (2,5 mg/day) from day 3 of cycle resulted in significant reduction in basal (by 53%) and surge levels of estrogen (by 70%) but this had no effect on follicular maturation, ovulation and luteal function as assessed by serum hormone profiles as well as laparotomy. This lack of need for estrogen for completion of follicular maturation process was confirmed by administering cycling monkeys hFSH (25 IU/day) from day 3 till day 8 of the cycle along with (5 mg Al/day) or without Al (n=3/group). Administration of AI resulted in suppression of FSH induced increase in serum estrogen (by 100%) and elevation in circulating androstenedione. Aromatase inhibitor treatment had no effect on either the number of follicles developed or their size relative to control. Testing the ability of both granulosa and thecal cells, removed on day 9 of treatment cycle, to respond to gonadotropinsin vitro showed no change indicating that cellular development and maturation of follicular cells had occurred normally. It is concluded that follicular maturation in the primate can occur even when increase in estrogen synthesis is blocked.