Follicle-stimulating hormone regulates in vivo testicular phosphodiesterase

The effect of FSH on testicular phosphodiesterase was studied in immature rats in order to verify that the regulation of response to hormone in the gonad involves an increased cyclic AMP catabolism. Hydrolysis of cyclic AMP and cyclic GMP was measured in the homogenates of seminiferous tubules and interstitium of control animals and animals injected i.p. with 50 micrograms ovine FSH twice, 24 h and 12 h before necroscopy. After hormonal treatment, cyclic AMP phosphodiesterase activity in the seminiferous tubules was markedly increased whether results were expressed per testis or per mg protein, while cyclic GMP phosphodiesterase present in the same compartment was apparently unaffected. In the interstitium, cyclic nucleotide hydrolysis was usually decreased after FSH injection. The stimulation of phosphodiesterase, a slow process reaching maximal stimulation after 12 h, was dependent on the dose of FSH injected. In addition, DEAE-cellulose chromatography of cytosol prepared from control and treated seminiferous tubules confirmed that stimulation was restricted to a cyclic AMP hydrolysing enzyme while the activity of the cyclic GMP hydrolysing form was not modified. Thus it is demonstrated that testicular phosphodiesterase is under FSH control. It is proposed that this in vivo regulation is a relevant phenomenon in the modulation of Sertoli cell function and contributes to the refractoriness that follows gonadotropin treatment.