Variation in the Effect of a Nongonadotropic Leydig Cell Stimulating Factor in Testicular Interstitial Fluid After Exposure of the Testis to a Single Episode of Heat Treatment

The activity of a nongonadotropic factor present in rat testicular interstitial fluid and capable of stimulating Leydig cell testosterone production was measured at intervals for 8 weeks after exposure of the testis to a single episode of heat treatment (43 C for 15 minutes). The activity of this factor was determined using a Leydig cell bioassay and the testicular albumin space (a measure of the interstitial fluid volume) was determined after the injection of 125I-labeled bovine serum albumin. Additionally, the response of interstitial cells to hCG stimulation was measured at each time point after heat treatment. The response of interstitial cells to hCG and the activity of the interstitial fluid were both increased transiently 2 or 3 weeks after heat treatment coincident with the disruption of spermatogenesis. These data provide further evidence for the local interaction of the tubules and interstitium and imply a role for the testicular interstitial fluid factor in these local regulatory mechanisms.