Effects of inhibin from primate Sertoli cells on follicle-stimulating hormone and luteinizing hormone release by perifused rat pituitary cells

We used a pituitary cell perifusion system to investigate the time course and selectivity of the inhibin effect on pulsatile GnRH-stimulated LH and FSH release. Dispersed pituitary cells from 7- to 8-week-old male rats were perifused on a Cytodex bead matrix and stimulated with 10 nM GnRH for 2 min every hour for 8-11 h. The addition of a preparation of inhibin partially purified from primate Sertoli cells reduced pulsatile FSH release within 2 h. After removal of inhibin from the perifusion medium, the effect was reversed within 3 h. GnRH-stimulated LH release was also influenced by inhibin, although the decline in LH was less than that in FSH (80 +/- 3% vs. 68 +/- 4% of control; P less than 0.025). Smaller doses of inhibin suppressed GnRH-induced FSH secretion, but had no effect on LH release. Further, prolonged incubation of pituitary cells with inhibin at the higher dose reduced its FSH inhibitory effect and eliminated the effect on LH. These results indicate that inhibin can reduce both LH and FSH secretion in vitro, although the specificity and magnitude of the effect are a function of both the dose and duration of inhibin treatment. Further, the actions of inhibin and GnRH on the pituitary may be interrelated.