title: Androgens directly stimulate spermatogonial differentiation in juvenile Atlantic salmon (Salmo salar).
abstract: We studied the effects of androgens on early stages of spermatogenesis along with androgen receptor binding characteristics and the expression of selected testicular and pituitary genes. To this end, immature Atlantic salmon postsmolts received testosterone (T), adrenosterone (OA, which is converted in vivo into 11-ketotestosterone, 11-KT) or a combination of the two androgens (T+OA). Treatment with OA and T elevated the plasma levels of 11-KT and T, respectively, and co-injection of OA with T lead to high 11-KT levels but prevented plasma T levels to reach the levels observed after injecting T alone. Clear stimulatory effects were recorded as regards pituitary lhb and gnrhr4 transcript levels in fish receiving T, and to a lesser extent in fish receiving OA (but for the lhb transcript only). The two androgen receptors (Ara1 and Ara2) we cloned bound T and 11-KT and responded to these androgens in a similar way. Both androgens down-regulated testicular amh and increased igf3 transcript levels after 1 week of treatment, but effects on growth factor gene expression required sustained androgen stimulation and faded out in the groups with the decreasing T plasma levels. In fish exhibiting a sustained elevation of 11-KT plasma levels (OA and T+OA groups) for 2 weeks, the number of differentiating spermatogonia had increased while the number of undifferentiated spermatogonia decreased. Previous work showed that circulating gonadotropin levels did not increase following androgen treatments of gonad-intact immature male salmonids. Taken together, androgen treatment of immature males modulated testicular growth factor expression that, when sustained for 2 weeks, stimulated differentiation, but not self-renewal, of undifferentiated type A spermatogonia.
authors.affiliation: Federal University of Minas Gerais, Institute of Biological Sciences, Department of Morphology, Av. Antônio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil; Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Melo
authors.affiliation: Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
authors.forename: Petra
authors.initials: P
authors.lastname: van Dijk
authors.affiliation: Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway.
authors.forename: Eva
authors.initials: E
authors.lastname: Andersson
authors.affiliation: University of Bergen, Postboks 7800, 5020 Bergen, Norway; Uni Research, Thormøhlens Gate 55, 5008 Bergen, Norway.
authors.forename: Tom Ole
authors.initials: TO
authors.lastname: Nilsen
authors.affiliation: Institute of Marine Research, Matre Research Station, 5984 Matredal, Norway.
authors.forename: Per Gunnar
authors.initials: PG
authors.lastname: Fjelldal
authors.affiliation: University of Bergen, Postboks 7800, 5020 Bergen, Norway.
authors.forename: Rune
authors.initials: R
authors.lastname: Male
authors.affiliation: Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Nijenhuis
authors.affiliation: Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: Bogerd
authors.affiliation: Federal University of Minas Gerais, Institute of Biological Sciences, Department of Morphology, Av. Antônio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Luiz Renato
authors.initials: LR
authors.lastname: de França
authors.affiliation: Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway.
authors.forename: Geir Lasse
authors.initials: GL
authors.lastname: Taranger
authors.affiliation: Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands. Electronic address: r.w.schulz@uu.nl.
authors.forename: Rüdiger W
authors.initials: RW
authors.lastname: Schulz
mesh_terms: D000728:Androgens / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism; D020317:Salmo salar / Q000235:genetics / Q000502:physiology*; D013091:Spermatogenesis / Q000187:drug effects / Q000235:genetics; D013093:Spermatogonia / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000378:metabolism; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000728:Androgens; D012333:RNA, Messenger; D011944:Receptors, Androgen; D013739:Testosterone; C003600:11-ketotestosterone
keywords: Androgens; Gene expression; Growth factors; Spermatogonia; Testis