title: Interleukin-1 stimulates deoxyribonucleic acid synthesis in immature rat Leydig cells in vitro.
abstract: The number of interstitial macrophages in the testis fluctuates according to age, increasing gradually during prepubertal development to reach 15-20% in the interstitial compartment in the adult rat. These macrophages are in close morphological association with Leydig cells. Macrophage products, interleukin-1 (IL-1) and tumor necrosis factor alpha stimulate and/or inhibit steroid production in cultures of Leydig cells. We have studied the effects of macrophage products on DNA synthesis in rat Leydig cells to investigate a possible paracrine role of testicular macrophage products on the proliferation of Leydig cells. Leydig cells isolated from 10-, 20-, and 70-day-old rats were cultured for 48 h in serum-free medium, washed, and treated with different cytokines for 18 h. The medium was then removed, fresh medium containing 0.5 microCi [3H]thymidine was added, and cells were incubated for 4 h prior to determining the incorporation of [3H]thymidine into DNA. Human recombinant IL-1 beta caused a dose-dependent stimulation in the incorporation of [3H]thymidine into DNA in the Leydig cells from 10- and 20-day-old rats but had no effect on DNA synthesis in interstitial cells from adult rats. Maximum stimulation of DNA synthesis in immature Leydig cells was observed with 1-2 ng/ml IL-1 beta. Autoradiography after incubation with [3H]thymidine showed a dramatic increase in the number of labeled Leydig cells after treatment with IL-1 beta (19.27 +/- 3.77% vs. 1.44 +/- 0.52% in control cultures) indicating that IL-1 beta recruited more cells to enter the cell cycle and initiate DNA synthesis. Human recombinant IL-1 alpha and tumor necrosis factor alpha also caused significant stimulation of DNA synthesis in Leydig cells but these cytokines were much less potent (1-10%) than IL-1 beta. IL-1 beta enhanced the effects of maximally effective concentrations of growth-promoting agents previously known to stimulate DNA synthesis in immature rat Leydig cells, i.e. human CG, steroidogenesis-inducing protein, and transforming growth factor alpha plus insulin. On the basis of these results it is concluded that IL-1 may play an important role in the proliferation of Leydig cells during prepubertal development in immature rats.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
authors.forename: S A
authors.initials: SA
authors.lastname: Khan
authors.forename: S J
authors.initials: SJ
authors.lastname: Khan
authors.forename: J H
authors.initials: JH
authors.lastname: Dorrington
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism*; D001345:Autoradiography; D002452:Cell Count / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D007375:Interleukin-1 / Q000494:pharmacology*; D007985:Leydig Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D004247:DNA