Demonstration of a nonsteroidal factor in human follicular fluid that attenuates the self-priming action of gonadotropin-releasing hormone on pituitary gonadotropes

The self-priming effect of gonadotropin-releasing hormone (GnRH) on luteinizing hormone (LH) release can be demonstrated in vitro by perfusing pituitary tissue with a continuous GnRH stimulus. A characteristic biphasic response is produced. We have used this system to investigate whether or not human follicular fluid (hFF) contains a nonsteroidal substance that can attenuate the GnRH-induced LH secretion in perfused rat pituitary glands. Steroid-extracted hFF, added to the perfusing medium, attenuated the self-priming action of GnRH in a dose-dependent manner. This was not abolished by selectively depleting the inhibin content of hFF by 97% on an immunoaffinity column. Furthermore, the biological activity of the substance was resistant to heating and was removed by dialysis. It is concluded that hFF contains a nonsteroidal factor, distinct from inhibin, that can attenuate the self-priming action of GnRH on pituitary gonadotropes.