The long-range objective of this research is to understand the structure, function and regulation of gonadotropin (luteinizing hormone, LH, or human choriogonadotropin, hCG) receptors in cultured Leydig tumor cells. Current studies are aimed at: (1)\characterizing the molecular structure of the gonadotropin receptors; and (2)\studying the mechanisms involved in the regulation of gonadotropin receptors by homologous and heterologous hormones.