Ontention of antisera against a hypothalamic decapeptide (luteinizing hormone/follicle stimulating hormone releasing hormone) which stimulates the release of pituitary gonadotropins and development of its radioimmunoassay

Using the classical approach, a decapeptide was synthesized with the structure of porcine luteinizing hormone/follicle stimulating hormone releasing hormone reported by Matsuo, H., Baba, Y., Nair, R. M. G., Arimura, A. and Schally, A. V. (1971) Biochem. Biophys. Res. Commun. 43, 1393–1399. As already reported, this peptide was capable of inducing in vitro the release of luteinizing hormone and follicle stimulating hormone from rat pituitary glands. A specific antiserum against luteinizing hormone/follicle stimulating hormone releasing hormone has been generated in the guinea pig and this allowed the development of a radioimmunoassay for this peptide. The antisera, at a final dilution of to depending on the antiserum used, were able to bind 35% of the ¹³¹I-labelled antigen. The sensitivity of this assay method was 50 pg of luteinizing hormone/follicle stimulating hormone releasing hormone. The following substances did not cross-react: oxytocin, lysine-vasopressin, synthetic thyroid stimulating hormone releasing hormone, ovine luteinizing hormone, follicle stimulating hormone and prolactin. Des-Trp³ luteinizing hormone/follicle stimulating hormone releasing hormone, pyroglutamyl-histidyl-tryptophan and seryl-tyrosyl-glycyl-leucyl-arginyl-prolyl-glycinamide, exhibited flatter curves than luteinizing hormone/follicle stimulating hormone releasing hormone with a cross-reactivity of about . Using this method, luteinizing hormone/follicle stimulating hormone releasing hormone was assayed in extracts of the sheep stalk-median eminence and of the hypothalamus and in jugular vein blood from a normal ram and from normal male rats, from cyclic ewe and from hypophysectomized ram and rats. It was concluded that luteinizing hormone/follicle stimulating hormone releasing hormone is present in hypothalamic extracts and in plasma of sheep and rat.