Characteristics of Hybrids of Ovine LH and Human Glycoprotein Hormone Subunits in Rat and Chicken in vitro Test Systems

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Abstract
Hybrids of ovine luteinizing hormone (oLH) and human chorionic gonadotropin (hCG) subunits were prepared and characterized. Human luteinizing hormone (hLH), hCG, oLH, and the hybrid gonadotropins hCGα:oLHβ and oLHα:hCGβ were tested for biological potency using three assays: 1) rat testis radioreceptor assay, 2) rat Leydig cell steroidogenesis assay, and 3) rooster testis steroidogenesis assay. In each assay the hybrid gonadotropins behaved characteristically as the parent gonadotropins from which the beta subunits were obtained. In the rat testis radioreceptor assay, hCG and oLHα:hCGβ were about 3 times as potent as oLH and hCGα:oLHβ. When assayed using the rat Leydig cell steroidogenesis assay, hCG and oLHα:hCGβ were about 1.25 times as potent as oLH and hCGα:oLHβ. In the rooster testis steroidogenesis assay, oLH and hCGα: oLHβ were about 300 times more potent than hCG or oLHα:hCGβ. The hLH behaved similarly but not identical to hCG in each assay system.