Constitutive expression of interleukin-1α messenger ribonucleic acid in rat sertoli cells is dependent upon interaction with germ cells

Interleukin-1 (IL-1), a proinflammatory cytokine originally isolated as a product of activated mononuclear phagocytes, consists of two distinct agonist proteins, IL-1 alpha and IL-1 beta, of which IL-1 beta is the major inducible IL-1 protein produced by macrophages. We show here that mRNA of IL-1 alpha, but not IL-1 beta, is constitutively expressed by the intact rat testis and localize the transcript to Sertoli cells as confirmed by a novel squash technique. The expression is developmentally regulated and appears only after postnatal day 20 in the rat testis, corresponding to onset of puberty. IL-1 alpha mRNA shows a stage-de pendent expression pattern during the cycle of the seminiferous epithelium. It is low or absent in stage VII, but present in all other stages of the cycle. The same stage-dependent distribution was also observed at the protein level when bioactive IL-1 was measured in extracts of accurately defined one millimeter segments of seminiferous tubules. No IL-1 alpha mRNA was detected in adult rat testes after germ cell depletion by fetal irradiation or cytostatic drug treatment. Because stage VII is the only segment of the seminiferous tubules lacking DNA replication, we propose that IL-1 alpha is involved in this event during mitosis and meiosis of spermatogenesis and that its expression is dependent upon interactions between Sertoli cells and germ cells.