Estradiol-induced increase of the LH responsive to LH releasing hormone (LHRH) in rat anterior pituitary cells in culture.

The effect of 17 beta-estradiol (E2) on LH secretion was studied using rat adenohypophyseal cells in primary culture. Preincubation of cells with 1 X 10(-9) M E2 for 40 h decreased the concentration of LHRH required for half-maximal stimulation (ED50) of LH release from 3.0 +/- 0.3 to 1.6 +/- 0.2 X 10(-10)M (P less than 0.01). Basal LH release was increased from 84 +/- 4 to 182 +/- 8 ng LH-RP-1/ml/4h (P less than 0.01) by E2 pretreatment. Time-course experiments showed that the stimulatory effect of 10(-8)M E2 on the LH response to LHRH can be first measured after 10 h of incubation in the presence of E2 and that this effect is maximal after 24 h of incubation with the steroid. While E2 increases the LH responsiveness to LHRH, androgens decrease the sensitivity of LH-secreting cells to the neurohormone. The LHRH ED50 value of testosterone-treated cells is of 7.2 +/- 0.4 vs. 3.7 +/- 0.3 X 10(-10)M for control cells (P less than 0.01). E2 can only partially reverse this inhibitory effect of androgens on the LH response to LHRH. These data show clearly that E2 can have a direct stimulatory effect on LH-secreting cells to increase the sensitivity of their response to LHRH.