A new function for the LH/CG receptor: Transcytosis or hormone across the endothelial barrier in target organs

Gonadotropins cross the vascular endothelial barrier to reach their target organs. Hormone concentrations in blood are very low and fluctuate rapidly to give sharp biological effects. Nonspecific transendothelial transport me chanisms are slow and markedly concentration dependent. There is thus a nee d for specific transendothelial transport mechanisms for these hormones. We will describe a specific transcytosis mechanism involving endothelial lutr opin/chorionic gonadotropin (LH/CG) receptors identical to those observed i n the target Leydig cells. A new role for the LH/CG receptor as a transcyto tic carrier of its ligands in endothelial cells is suggested.