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Homologous desensitization of rat Sertoli cells by non‐stimulating concentrations of follicle‐stimulating hormone

Pre‐incubation of rat Sertoli cells with concentrations of follicle‐stimulating hormone (FSH) too low to stimulate plasminogen activator (PA) secretion, provoked an inhibition of its subsequent stimulation by an effective dose of the hormone. A kinetic study of this desensitization was performed using equine FSH (which exhibits prolonged stimulation of PA secretion) and porcine FSH (which like all other FSH tested, provokes a transient response). Low non‐stimulating concentrations of both hormones were shown to inhibit the subsequent PA response to each of them. Desensitization of rat Sertoli cells by low (non‐stimulating) concentrations of FSH did not modify the typical time course (transient or prolonged) of PA secretion under subsequent stimulation by porcine or equine FSH, respectively. Only the intensity of the response to each hormone was dramatically reduced. Besides, the induction of desensitization by these non‐stimulating concentrations of FSH was shown to be very rapid (10‐15 min). The precise mechanism of this desensitization is not yet clear but its abolishment by the cyclic nucleotide phosphodiesterase (PDE) inhibitor MIX is consistent with the hypothesis that activation of PDE occurs at lower FSH concentration than adenylate cyclase activation.