RADIOIMMUNOASSAY OF LUTEINIZING HORMONE-RELEASING HORMONE (LH-RH) IN SERUM FROM MAN, SHEEP AND RAT

Abstract

A radioimmunoassay for luteinizing hormone-releasing hormone (LH-RH) has been developed. Antisera were raised against the decapeptide conjugated to albumin in rabbits and against the 3-10 octapeptide conjugated to albumin in rats. LH-RH was iodinated with ¹²⁵I and purified on Sephadex, the most immunoreactive fractions of the ¹²⁵I-LH-RH being eluted after ¹²⁵I. A serum assay was developed using a simple methanol extraction procedure. The rabbit antiserum could detect levels of LH-RH in the jugular vein of the sheep at various times and in the rat on the afternoon of pro-oestrus. The assay using the rat antiserum was 30 times more sensitive and could detect LH-RH in peripheral serum in man. 10-20 pg/ml in peripheral serum of man, but the RIA could be used to measure the disappearance and clearance of LH-RH after intravenous injection of large test doses (Jeffcoate et al. 1974a). In this study we describe the details of a RIA of LH-RH in serum from man, sheep and rat.