The synthetic gestagen levonorgestrel directly affects gene expression in thyroid and pituitary glands of Xenopus laevis tadpoles.
The synthetic gestagen levonorgestrel (LNG) was previously shown to perturb thyroid hormone-dependent metamorphosis in Xenopus laevis. However, so far the mechanisms underlying the anti-metamorphic effects of LNG remained unknown. Therefore, a series of in vivo and ex vivo experiments was performed to identify potential target sites of LNG action along the pituitary-thyroid axis of X. laevis tadpoles. Prometamorphic tadpoles were treated in vivo with LNG (0.01-10nM) for 72h and brain-pituitary and thyroid tissue was analyzed for marker gene expression. While no treatment-related changes were observed in brain-pituitary tissue, LNG treatment readily affected thyroidal gene expression in tadpoles including decreased slc5a5 and iyd mRNA expression and a strong induction of dio2 and dio3 expression. When using an ex vivo organ explant culture approach, direct effects of LNG on both pituitary and thyroid gland gene expression were detecTable Specifically, treatment of pituitary explants with 10nM LNG strongly stimulated dio2 expression and concurrently suppressed tshb expression. In thyroid glands, ex vivo LNG treatment induced dio2 and dio3 mRNA expression in a thyrotropin-independent manner. When thyroid explants were cultured in thyrotropin-containing media, LNG caused similar gene expression changes as seen after 72h in vivo treatment including a very strong repression of thyrotropin-induced slc5a5 expression. Concerning the anti-thyroidal activity of LNG as seen under in vivo conditions, our ex vivo data provide clear evidence that LNG directly affects expression of genes important for thyroidal iodide handling as well as genes involved in negative feedback regulation of pituitary tshb expression.
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany. Electronic address: claudia.lorenz@igb-berlin.de.
Claudia
C
Lorenz
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Institute of Interdisciplinary Research in Molecular Human Biology (IRIBHM), Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium.
Robert
R
Opitz
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Institute of Interdisciplinary Research in Molecular Human Biology (IRIBHM), Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium.
Achim
A
Trubiroha
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
Ilka
I
Lutz
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
Andrea
A
Zikova
Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany; Department of Endocrinology, Institute of Biology, Humboldt University Berlin, Germany.
Werner
W
Kloas
D000818:Animals; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D007814:Larva / Q000187:drug effects; D016912:Levonorgestrel / Q000633:toxicity*; D008297:Male; D008675:Metamorphosis, Biological / Q000187:drug effects; D010902:Pituitary Gland / Q000187:drug effects*; D011372:Progestins / Q000235:genetics; D027981:Symporters / Q000235:genetics; D013961:Thyroid Gland / Q000187:drug effects*; D013972:Thyrotropin / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000633:toxicity; D014982:Xenopus laevis / Q000254:growth & development / Q000502:physiology*; D000099209:Sodium-Iodide Symporters
D016912:Levonorgestrel; D011372:Progestins; D027981:Symporters; D013972:Thyrotropin; D014874:Water Pollutants, Chemical; D000099209:Sodium-Iodide Symporters
Deiodinase; Ex vivo organ culture; NIS; Pituitary-thyroid axis; Progestin; TSH; Xenopus laevis