Steroid exposure during larval development of Xenopus laevis affects mRNA expression of the reproductive pituitary-gonadal axis in a sex- and stage-dependent manner.
Steroids are known to influence the reproductive pituitary-gonadal axis in adult amphibians. Here, we studied the effects of hormones on pituitary and gonadal mRNA expression during the development of Xenopus laevis. Tadpoles at NF 58 (prometamorphosis) and at NF 66 (freshly metamorphosed) were exposed for three days to 17β-estradiol (E2), tamoxifen (TAM), testosterone (T), dihydrotestosterone (DHT) at 10(-7)M, and flutamide (FLU) at 10(-6)M. In both genders at NF 58 and 66, T and DHT decreased luteinizing hormone beta (lhβ), but increased follicle stimulating hormone beta (fshβ), while FLU induced lhβ specifically in males. In the testis steroidogenic genes (p450 side chain cleavage enzyme, p450scc; steroid acute regulatory protein, star) at NF 58 showed a similar pattern as for lhβ, while the response at NF 66 was only partially present. In females, TAM induced lhβ at NF 58, while E2 decreased lhβ and increased fshβ at NF 66. In the ovaries, no alterations were observed for the steroidogenic genes. Summarizing, gonadotropic and steroidogenic mRNA expression may indicate control of androgen level during testis differentiation in male tadpoles at NF 58. In females the non-responsiveness of steroidogenic genes could be a sign of gonadal quiescence during pre-pubertal stages.
CIIMAR, Centre of Marine and Environmental Research, Laboratory of Ecotoxicology, Genomics and Evolution, Rua dos Bragas 289, 4050-123 Porto, Portugal. Electronic address: rurbatzka@ciimar.up.pt.
Ralph
R
Urbatzka
Department of Ecophysiology and Aquaculture, Leibniz-Institute for Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
Claudia
C
Lorenz
Reproduction Biology, Leibniz-Institute for Zoo and Wildlife Research, PF 601103, 10252 Berlin, Germany.
Caterina
C
Wiedemann
Department of Ecophysiology and Aquaculture, Leibniz-Institute for Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
Ilka
I
Lutz
Department of Ecophysiology and Aquaculture, Leibniz-Institute for Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany; Department of Endocrinology, Institute of Biology, Humboldt-University, Berlin, Germany.
Werner
W
Kloas
D000818:Animals; D005260:Female; D006066:Gonads / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D008297:Male; D010053:Ovary / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis*; D012727:Sex Characteristics; D013256:Steroids / Q000633:toxicity*; D013737:Testis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D014982:Xenopus laevis
D012333:RNA, Messenger; D013256:Steroids
Feedback mechanism; Follicle-stimulating hormone beta; Hypothalamus–pituitary–gonadal axis; Luteinizing hormone beta; Reproductive development; Steroidogenesis