Repeated injections of synthetic LH RH adsorbed on polyvinylpryrrolidone and mixed with Freund's adjuvant to rabbits resulted in production of specific antiserum to LH RH. Rabbits which produced this antiserum had reduced pituitary LH content and marked atrophy of the testes. The antiserum binds purified 125I LH RH. LH RH iodinated by chloramine T or lactoperoxidase method was purified on CMC column. Three peaks of radioactivity were eluted: unreacted iodide; labelled product with little affinity to the antiserum; and labelled LH RH which binds to the antiserum. The specific activity of 125I LH RH was 320 μc/μg. When traces of cold LH RH (<0.31 ng) were added, the binding of 125I LH RH to the antiserum was increased, a phenomenon known as paradoxical binding. With greater doses of cold LH RH, an ordinary standard curve of radioimmunoassay (RIA) was obtained. Two RIA systems for LH RH were established: RIA in which 125I LH RH was mixed with 0.31 ng LH RH before incubating with antiserum and samples. This method leads to an ordinary standard curve; RIA using paradoxical binding. In the former, minimum detectable dose was 40 pg; in the latter, 4 pg. The antiserum showed no cross reaction with other hypothalamic and pituitary hormones. Standard curves for rat hypothalamic extracts and purified human LH RH were superimposable on the curves for LH RH decapeptide. This validates the RIA methods and suggests that rat and human LH RH is also (pyro) Glu His Trp Ser Tyr Gly Leu Arg Pro Gly NH2.
|Original language||English (US)|
|Number of pages||1|
|Issue number||3 (I)|
|State||Published - Jan 1 1973|
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