Isolation and partial characterization of an interleukin-1-like factor from rat testis interstitial fluid

Testicular interstitial fluid (ISF) was collected by in vivo perfusion of rat testes and analyzed for the presence of interleukin-1 (IL-1) activity by utilizing a murine thymocyte proliferation assay. IS obtained from nine rats were all positive with dose-response curves of IL-1 activity similar to those produced by rat testicular aqueous extracts, rat macrophage IL-1 and human recombinant IL-1 alpha. Chromato-focusing of pooled ISF revealed a single peak of IL-1 activity with an estimated isoelectric point of 6.1-6.3. HPLC size exclusion chromatography demonstrated two active peaks with apparent molecular ratios Mr of 15,000-18,000 and 5000-7000, respectively. The molecular properties of the 15,000-18,000 Mr component are very similar to those of an IL-1-like factor previously isolated from seminiferous tubules. Our results indicate that the testicular IL-1-like factor is secreted by the seminiferous tubules into the interstitial tissue. Its function in the testicular interstitium is unknown but it might be relevant for the tendency to testicular relapse of childhood lymphocytic leukemia.