FUNCTION OF INTERLEUKIN-6 AS AN INHIBITOR OF MEIOTIC DNA-SYNTHESIS INTHE RAT SEMINIFEROUS EPITHELIUM

Interleukin-6 bioactivity (IL-6) has been shown to be present in Serto li cells. To further characterize the IL-6 in the seminiferous epithel ium, the IL-6 like-antigen was detected, stage-specific basal distribu tion of IL-6-like bioactivity and its regulation by FSH, cAMP and TPA was characterized in isolated, rat seminiferous tubule segments. In ad dition, the effects of human recombinant IL-6 on stage-specific DNA sy nthesis was investigated. Both monoclonal and polyclonal antibodies re cognized M(r) 22 and 23 kDa of IL-6 like immunoreactivity in the semin iferous epithelium. The basal IL-6 production showed high levels durin g stages XIII-XIV-I-V, low during VII and VIII. FSH stimulated IL-6 pr oduction at nearly all stages and most significantly at stage VII of t he cycle. Human recombinant IL-6 dose-dependently inhibited the onset of meiotic DNA synthesis of preleptotene spermatocytes, and a minor in hibition was found on advanced (A(3)-type B) spermatogonia. These resu lts support the hypothesis that IL-6 is a stage-specific paracrine reg ulator of the seminiferous epithelium exerting a specific inhibitory a ction on meiotic DNA synthesis.