The involvement of insulin-like growth factor-I in local control of steroidogenesis and DNA synthesis of Leydig and non-Leydig cells in the rat testicular interstitium.
Insulin-like growth factor-I (IGF-I) peptide, receptors and binding proteins are present in the rodent testis, which strongly implies that IGF-I has one or more testicular functions. In the present study we provide further information to support the concept that IGF-I is an important local mediator in the testis. High concentrations of IGF-I were measurable in interstitial fluid by radioimmunoassay, and IGF-I-binding proteins (IGFBPs) were readily detectable in interstitial fluid by ligand blotting, the predominant type being IGFBP-2. In vitro, IGF-I bound to testicular interstitial cells which did not have 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity and which were resistant to ethane dimethanesulphonate treatment. In vitro, IGF-I receptor-mediated actions increased both steroidogenesis and DNA synthesis. Insulin stimulated DNA synthesis at concentrations appropriate to cross-react with the IGF-I receptor, and this effect was greater in a testicular interstitial Leydig cell-depleted cell population compared with a Leydig cell-enriched cell culture. Furthermore, combinations of epidermal growth factor or transforming growth factor -alpha together with insulin appeared to act synergistically, causing extremely large increases in [3H]thymidine incorporation in the interstitial cells. These results support a paracrine and/or autocrine role for IGF-I in interstitial cell growth and development.
Moore
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Department of Physiological Sciences, University of Manchester, U.K.
Morris
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ID
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D004247:DNA / Q000032:analysis / Q000096:biosynthesis*; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism; D018971:Insulin-Like Growth Factor Binding Protein 2; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D007985:Leydig Cells / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D008024:Ligands; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013737:Testis / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D013739:Testosterone / Q000032:analysis / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D008024:Ligands; D014316:Tritium; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017526:Receptor, IGF Type 1; D013936:Thymidine