Constitutive production of interleukin-1α mRNA and protein in the developing rat testis

Interleukin-1 (IL-1), a multifunctional cytokine produced mainly by activated macrophages, is also produced in the intact testis. Rat testicular IL-1 was found to be identical to IL-1 alpha, judged by immunoneutralization of the bioactive protein and sequence comparison of cloned rat testicular and macrophage pro-IL-1 alpha cDNA. Testicular IL-1 alpha mRNA was first demonstrated on postnatal day 15, and the corresponding bioactive protein from day 20. IL-1 alpha mRNA was still low on day 20, but then increased rapidly in parallel with the bioactive protein to establish a plateau level from day 25. In adult testes, IL-1 alpha mRNA and immunoreactive protein were low in stage VII of the seminiferous epithelial cycle, whereas other stages showed a clearly detectable expression. In the adult testis, the concentration of IL-1 alpha was 75 pg/mg testicular protein (approximately 200 pM). In conclusion, production of testicular IL-1 alpha is developmentally and stage-dependently regulated, probably at the transcriptional level, emphasizing an important paracrine role in testicular function.