Regulation of interstitial cell function by seminiferous tubules in intact and cryptorchid rats

The effects of experimental cryptorchidism on seminiferous tubule secretions and interstitial cell testosterone production were studied in vitro. Spent media obtained from incubations of seminiferous tubules (SMST) from cryptorchid rats caused a significant increase in testosterone production when added to interstitial cells isolated from intact rats. The previously noticed inhibitory activity of the SMST from stages VIII-XI of the spermatogenic epithelial cycle gradually disappeared after the induction of experimental cryptorchidism. SMST obtained from both sham-operated or cryptorchid rats stimulated basal testosterone production when added to interstitial cells from cryptorchid rats. SMST from rats had been cryptorchid for 7, 14 and 28 days stimulated testosterone production when added to interstitial cells prepared from intact animals. Seminiferous tubules from cryptorchid rats therefore appear to be the source of a heat stable, trypsin-resistant factor with an apparent molecular weight of between 5000 and 10,000 daltons which stimulates testosterone production when added to interstitial cells in vitro. Its activity could not be blocked by an LRH antagonist. This factor enhances both basal and LH-stimulated secretion of testosterone in contrast to the inhibitory activity which involves only a partial blockade of LH-dependent steroidogenesis.