Differential Feedback Regulation by 17β-Estradiol of LH Production and LHRH-Responsiveness in Adenohypophyseal Cell Cultures

To evaluate the direct effects of 17β-estradiol (E2) on pituitary LH release, cellular LH content, and LHRH-gesponsive-ness, physiological doses of E2 (10−10, 10−9, or 10−8M) were tested in pituitary monolayer cultures of female rats. The effects of E2 appeared to be dose-related. After a4 h incubation, basal LH release was significantly stimulated by lO−10M E2 (176% of control level) whereas 10−10M or 10−8M had no effect. The cellular LH content was significantly stimulated by 10−8M E2 (127% of control level) but not by the lower doses of E2. Both 10−8M and 10−9m E2 but not 10−10M E2 stimulated LH production (sum of LH contents in medium and cells). When the cultures were incubated with 10−8M LHRH, cellular LH content was depressed (76% of control level) by 10−8M E2 coincubation, whereas LH release was not altered. To further explore the interaction between E2 and LHRH, extended preincubation times with 10−8M E2 were used to test its effect on the subsequent LHRH-responsiveness. After a lag period, prein...