Abstract
Exposure of rat Leydig cells to high doses of LH/hCG in vivo results in a dose-dependent and temporary desensitization of the androgenic and cAMP response to LH/hCG when tested in vitro [l, 21. The same high doses of LH/hCG reduce the concentration of LH/hCG receptors on testicular membrane particles [3-51. Such decrease in the concentration of LH/hCG receptors may reduce sensitivity to LH/hCG [1, 23. The present paper provides indirect evidence for an additional mechanism by which LH/hCG may cause Leydig cell desensitization by either directly or indirectly stimulating the intracellular levels of phosphodiesterase (PDE) and thus reducing the magnitude of the cAMP response.