A rapid,sensitive bioassay for luteinizing hormone-like gonadotropins

This report describes a simple and sensitive bioassay for gonadotropins having luteinizing hormone (LH)-like activity. The procedure depends on the ability of the gonadotropins to stimulate testosterone synthesis in testis interstitial cell suspensions prepared by collagenase digestion of immature rat testes. Although a similar procedure has been described previously, the method described here provides two modifications which (1) allow the chemically related gonadotropins LH and human chorionic gonadotropin (HCG) to be distinguished biologically and (2) increase the speed and reduce the cost of the assay. As described, the assay can be utilized to measure gonadotropin activity of avian, reptilian, amphibian, and, possibly, piscine materials as well as that of the well-characterized mammalian hormones. The simplicity and sensitivity (1 pg of HCG, 20 pg of LH) of this assay should greatly facilitate the isolation and purification of gonadotropins from nonmammalian vertebrates and, thus, enable comparative studies which were heretofore nearly impossible.