The specificity of an ovine pituitary incubation system linked with gonadotrophin assays for detecting gonadotrophin releasing activity.

Abstract

SUMMARY A sheep pituitary incubation system was developed which may be used to study the release of both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as assayed biologically. Specificity was examined by adding at high concentration various materials present in the hypothalamus, a crude acid extract of sheep cerebral cortex or crude or partly purified extracts of ovine hypothalamic tissue. Of the materials tested for LH and FSH releasing activity, oxytocin, adrenaline, synthetic lysine vasopressin and cerebral cortex extract failed to influence LH or FSH release. Natural vasopressin containing unknown proportions of the lysine and arginine forms did not affect FSH release but produced a significant increase in the LH content of the medium, the reason for which was not clear. Noradrenaline failed to influence FSH release but produced an apparent depression in the LH content of the medium due to an action on the LH released or upon the ovarian ascorbic acid depletion assay since the addition of noradrenaline to standard ovine LH reduced the potency in the assay to an almost identical degree. Extracts of ovine hypothalamic tissue consistently increased the LH and FSH content of the medium. The method described may be applicable to the detection and estimation of LH and FSH releasing activity in ovine hypothalamic tissue extracts and to detecting changes in the responsiveness to hypothalamic stimulation of sheep pituitary tissue.