Blockade of the estrogen-induced luteinizing hormone surge in monkeys: a nonsteroidal, antigenic factor in porcine follicular fluid.

That both follicular fluid extracts and ovarian hyperstimulation block estrogen-induced gonadotropin surges in primates has been established. In the present study, the differential actions of gonadotropin-releasing hormone (GnRH) and estradiol benzoate (E2B) on bioassayable LH (BIO-LH) secretion in the presence of a porcine follicular fluid (pFF) extract were assessed. Further, the inherent immunogenicity of the follicular fluid factor(s) that block estrogen-induced surges was examined. In castrated monkeys, administration of Florisil/charcoal-extracted pFF did not affect BIO-LH secretion induced by exogenous GnRH, although the pFF extract abolished E2B-induced BIO-LH surges. In monkeys given pFF chronically (for 6 to 8 months), immune responses capable of neutralizing the inhibitory actions of pFF on the E2B-induced BIO-LH surges developed. In these pFF-immunized monkeys, the BIO-LH surge induced by an E2B challenge was restored despite concurrent pFF injections.