Effect of human chorionic gonadotropin derivatives on Leydig cell function

Background: Several human chorionic gonadotropin (hCG) derivatives have bee n detected in healthy human subjects, indicating that they may play a role in cell function. These hCG derivatives include deglycosylated hCG, proteol ytic digestion products of hCG and free alpha and beta subunits of the horm one. It is well documented that testicular Leydig cells are responsive to l uteinising hormone (LH) or its analogue hCG. These hormones have high affin ity for LH/hCG receptors on the plasma membrane. Methods: We designed funct ional and binding studies to compare the effects of native hCG and several hCG derivatives on a rat Leydig cell system. The molecular weight of the hC G derivatives was determined by SDS-PAGE and the binding affinity to LH/hCG receptors was measured by a radioligand assay. In addition, their ability to produce testosterone, cyclic AMP and arachidonic acid release was also s tudied. Results: These hCG derivatives, with the exception of the free beta subunit, were able to bind to LH/hCG plasma membrane receptors with differ ent affinities than that of native hCG. In addition, hCG derivatives did no t increase intracellular cAMP levels or arachidonic acid release. However, they did increase testosterone production. Conclusion: Taken together, the results of this study lead us to suggest that these hCG derivatives may reg ulate the action of the native hormone in Leydig cells and are, thus, molec ules of physiological relevance. Copyright (C) 2001 S.Karger AG, Basel.