Interleukin-6 secretion from rat Leydig cells in culture.

Recent evidence indicates that interleukin-6 (IL-6) acts on Sertoli cells to modulate secretory function. IL-6 is also detected in medium bathing tissue or cells from the seminiferous tubule, suggesting a testicular regulatory role. Because other cytokines found to be active in testicular function have more than one site of production, we examined whether Leydig cells may serve as an alternate source of IL-6. Purified Leydig cells were cultured with or without modulatory substances, and the medium was subjected to the 7TD1 bioassay for IL-6. Northern analysis using an IL-6 cDNA probe was performed on companion cell preparations. Incubation with either hCG or IL-1 beta increased the levels of bioactive IL-6 released into the medium and IL-6 mRNA detected in the cells in a dose-related manner. When used together, these agents had an additive stimulatory influence on both the release of IL-6 bioactivity and the amount of IL-6 mRNA. Our results demonstrate that IL-6 is secreted from enriched preparations of Leydig cells and that its release is under the control of at least two modulators of testicular function. Identification of interstitial cells as a site of IL-6 production coupled with reports of IL-6 release and action in seminiferous tubular cell preparations suggest that IL-6 may serve a role in signal integration or communication from one testicular location to another.