Modulation of rat pituitary gonadotrophin secretion by porcine granulosa cell 'inhibin', LH releasing hormone and sex steroids in rat anterior pituitary cells in culture

Abstract

The incubation of female rat adenohypophysial cells in primary culture with porcine granulosa cell culture medium (GCM) led to the complete inhibition of responses of LH and FSH to LH releasing hormone (LHRH) as well as to the inhibition of spontaneous release of FSH. These effects of GCM suggest the specificity of the 'inhibin'-like activity of this material. Granulosa cell culture medium completely reversed the stimulatory effect of oestradiol-17β on the responses of LH and FSH to LHRH, as well as reversing the stimulatory effect of progesterone, oestradiol or a combination of both steroids on the spontaneous release of FSH, while not affecting the spontaneous release of LH. The antioestrogenic effects of progesterone observed on the response of LH to 0·3 nm-LHRH were amplified in the presence of GCM while the stimulatory effects of progesterone, oestradiol or both on the response of FSH to 0·3 nm-LHRH were completely reversed by the medium. Moreover, the presence of GCM led to an additive inhibitory effect with dihydrotestosterone on the response of LH to LHRH while it completely reversed the stimulatory effect of the androgen on spontaneous and LHRH-induced FSH release. The present data show that the presence of porcine granulosa cell 'inhibin' activity can exert marked interactions with sex steroids in the control of gonadotrophin secretion. This 'inhibin' activity reversed all the stimulatory effects and potentiated all the inhibitory effects of sex steroids on gonadotrophin secretion. Although the physiological role of 'inhibin' remains to be defined well, the importance of this activity is clearly demonstrated in anterior pituitary cells in culture. J. Endocr. (1984) 100, 133–140