INFLUENCE OF OESTROGEN ADMINISTRATION IN VIVO AND IN VITRO ON THE RELEASE AND SYNTHESIS OF LH AND FSH FROM INCUBATED PITUITARIES

Abstract

ABSTRACT The effect of oestrogen on the release and synthesis of LH and FSH was studied in rat adenohypophyses incubated for a period of 4 h in flasks containing 1 ml Eagle's medium. One hemipituitary was used as the experimental gland and the other half served as a control. The spontaneous release of LH and FSH by glands from ovarectomized rats was not affected by oestradiol-17β added to the incubation medium in doses of 55, 166, 500 and 1500 ng/ml. The amount of hormones released by pituitaries from spayed rats injected with oestradiol benzoate (2.5, 5.0 and 10.0 μg/rat) 2 h or 24 h before killing the animals too was not different from that of oil-injected rats. Neither was there any effect of oestrogen when added to the incubation medium of glands from oestrogen-pre-treated rats. However, the concentration of LH and FSH in the gland increased when oestrogen was added to the incubation medium, indicating enhanced synthesis. The effect was dose-dependent up to the dose of 500 ng/ml oestradiol but a dose of 1500 ng/ml was less effective. Increased synthesis of LH but not of FSH was also observed in incubated glands from rats injected with oestrogen 24 h before death, but no changes were seen in those of rats killed 2 h after treatment. Additive effects occurred with the in vivo and in vitro steroid treatment. These results indicate that oestrogen favours synthesis of LH and FSH in cultured pituitaries, without affecting gonadotrophin secretion and that the changes induced in the in situ gland by oestrogen treatment are reflected by their in vitro activity.