Rapid in vitro desensitization of the testosterone response in rat Leydig cells by sub-active concentrations of porcine luteinizing hormone.

We have studied in rat Leydig cells, the effect of sub-active concentrations of porcine LH on the subsequent stimulation of the cAMP and testosterone production by a sub-maximal concentration of pLH or hCG. We found that extremely low concentrations of pLH (0.01-2.0 ng/ml) were able to induce rapidly a partial but highly significative desensitization of the testosterone response without affecting the cyclic AMP response. These data indicate that desensitization of the steroidogenic response might be due to some lesion beyond cAMP formation or at the level of one discrete compartment of cyclic AMP, directly involved in the control of steroidogenesis. Moreover, our data strongly suggest that the basal circulating concentrations of LH can exert an inhibitory control on the testosterone response to LH pulses in vivo.