Low reversibility of intracellular cAMP accumulation in mouse Leydig tumor cells (MLTC-1) stimulated by human Luteinizing Hormone (hLH) and Chorionic Gonadotropin (hCG).

In order to study the intracellular cAMP response kinetics of Leydig cells to hormones with LH activity, we used MLTC-1 cells transiently expressing a chimeric cAMP-responsive luciferase so that real-time variations of intracellular cAMP concentration could be followed using oxiluciferin luminescence produced from catalyzed luciferin oxidation. The potencies of the different LHs and CGs were evaluated using areas under the curves (AUC) of their kinetics over 60 min stimulation. All mammalian LHs and CGs tested were found to stimulate cAMP accumulation in these cells.