Short-term effects of oestradiol and 4-hydroxyoestradiol on gonadotrophin-releasing hormone induced luteinizing hormone secretion by rat pituitary cells in culture.

Dispersed pituitary cells from adult female rats were preincubated for different time periods (0-12 h) in the absence or presence of 10(-9)M oestradiol (E2) or 4-hydroxyoestradiol (4-OHE2). Then the media were changed and the cells incubated for 4 h with either vehicle, or E2, or 4-OHE2 and additionally with different concentrations (10(-11)-10(-7) M) of gonadotrophin-releasing hormone (GnRH). Treatment of pituitary cells with E2 for 4 h (i.e. no preincubation with E2) significantly decreased the LH-response to GnRH at concentrations greater than or equal to 10(-10) M of the decapeptide. During a transition time of approximately 10 h (i.e. in cultures preincubated with E2 or vehicle for 2, 4, 6 or 8 h and then coincubated with E2 or vehicle and GnRH for 4 h) no differences between E2- and vehicle-treated cultures were observed. After 14 and 16 h of E2-treatment (i.e. 10 or 12 h preincubation and 4 h coincubation with GnRH) the LH-responses to GnRH in these cultures were significantly higher than in the respective controls. A nearly identical reaction pattern was observed when 4-OHE2 was used instead of E2. In a second series of experiments dispersed rat pituitary cells were suspended in a carrier gel and continuously perifused with medium, using small chromatography columns. When these cells were exposed for 4 min to 10(-9) M GnRH at 60 or 48 min intervals, they reacted with reproducible pulsatile LH-discharges during at least 6 subsequent stimuli with the decapeptide.(ABSTRACT TRUNCATED AT 250 WORDS)