Regulation of Interleukin-6 (IL-6) Messenger RNA Expression in Rat Leydig and Sertoli Cells In Vitro

Interleukin-6 (IL-6) is a cytokine involved in various biological activities. Recently, it was shown that IL-1, a potent inducer of IL-6, was produced by tests of rats and humans. In addition, it was demonstrated that rat Sertoli cells produced an IL-6-like factor (s) in vitro. In the present study, we demonstrated that specific cell types isolated from the tests of rats of different ages expressed 1.2 and 2.4 kb IL-6 mRNAs, and the multifactorial regulation of IL-6 mRNAs in Sertoli and Leydig cells was temporally and hormonally regulated in vitro.By using Northern hybridization techniques, IL-6 gene expression was not detected in pachytene spermatocyte or round spermatid. However, abundant levels of IL-6 mRNAs were demonstrated in adult Leydig cells isolated by Percoll purification. Although no IL-6 mRNAs could be detected in freshly isolated immature Leydig cells, these cells did express IL-6 mRNAs slightly at 3 h and obviously at 18 h in vitro. In addition, IL-6 mRNA levels were significantly increased by the addition of IL-1α or IL-1β, but not prolactin at 18 h. These levels were enhanced by hCG and the neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP) in early time at 3 h. Similarly, freshly isolated immature Sertoli cells contained exceedingly low to non-detectable levels of IL-6 mRNAs. These levels were significantly stimulated by FSH, PACAP, IL-1α and IL-β.The different time-courses of activation suggest that more than one mechanism of regulation for IL-6 production may exist in testicular cells. IL-6 may be a putative paracrine/autocrine factor mediating interactions among the different testicular cells in the seminiferous tubule and interstitium.