Direct effect of estradiol-17β on progesterone accumulation by ovarian granulosa cells from rhesus monkeys.

We have previously demonstrated that estradiol-17β (E) administered in vivo induces atresia of the dominant ovarian follicle (DF). Whether this effect is exerted directly at the ovarian level or by central mediation has not been confirmed. The present study was designed to assess whether E in amounts similar to those found in monkey follicular fluid (FF) directly alters in vitro progesterone (P) accumulation by granulosa cells (GC) aspirated from follicles in cycling rhesus monkeys. Follicular contents were aspirated from three to five animals on each of days 8-13 of the cycle. GC were plated at a density of 50,000 viable GC/0.5 ml medium; GC were incubated with 0 or 2-2,000 ng/ml E, and cultures were maintained for 72 h. P accumulation by GC collected on day 8 and treated with 2 ng/ml E was augmented 37.5 ± 5.5% (X ± S. E. M.; P<.05) over controls but was diminished significantly at 20 ng/ml ( -55 ± 18% with respect to controls), 200 ng/ml ( -73.7 ± 13.2%), and 2,000 ng/ml ( -77.3 ± 18.4%). A similar dose-response relationship was noted on other cycle days. At a concentration of 2,000 ng/ml, E significantly reduced P 91.5 ± 8.5% (day 10), 81.5 ± 18.5% (day 11), 84.3 ± 4.7% (day 12), and 53.7 ± 15.8% (day 13). We conclude that E at concentrations found in FF can inhibit P output by monkey GC through a direct action.