Effect of inhibin like factors on gonadotrophin release by the mouse pituitary in vitro.

The release of gonadotrophins by the mouse whole pituitary in vitro was investigated. Whole tissue from 34 day old male mice was highly responsive to synthetic LRH in short incubations at 37 degrees C. About 15% of FSH and 17% of LH were secreted during a 3 h pulse with 3 ng of LRH. Pre-exposure of the mouse pituitary to fractions containing inhibin activity, inhibited the FSH release induced by LRH. Inhibin from bovine and human seminal plasma and porcine follicular fluid preferentially inhibited FSH secretion, while LH secretion was also reduced by inhibin like factors from bovine follicular fluid and testicular extract. The inhibition of FSH and/or LH release was measured by specific radioreceptor assays and could not be due to destruction of either gonadotrophin or LRH. Purified bovine seminal plasma inhibin was effective at very low concentrations in vitro. The whole incubation system is simple and an estimation of inhibition of bioactive (binding activity) FSH release can be obtained within 24 h.