title: Molecular and histological endpoints for developmental reproductive toxicity in Xenopus tropicalis: Levonorgestrel perturbs anti-Müllerian hormone and progesterone receptor expression.
abstract: There is an increasing concern regarding the risks associated with developmental exposure to endocrine disrupting chemicals and the consequences for reproductive capability. The present study aimed to refine the Xenopus (Silurana) tropicalis test system for developmental reproductive toxicity by characterising molecular and histological features of sexual development, and to explore effects of exposure to the progestagen levonorgestrel (LNG). Larvae were exposed to LNG (0, 3, 30, 300 ng/L) over the first three weeks of development, encompassing the beginning of gonadal differentiation. mRNA levels of amh (anti-Müllerian hormone), amhr2 (amh receptor 2), ipgr (intracellular progesterone receptor), mpgr beta (membrane progesterone receptor beta), and cyp19a1 (cytochrome p450 19a1) were quantified in larvae and juveniles (4 weeks post-metamorphosis). Relative cyp19a1 and amh expression was used as a molecular marker for phenotypic sex of larvae. Gonadal and Müllerian duct development were characterised histologically in juveniles. Compared to controls, LNG exposure increased the expression of amh and ipgr in male larvae. In juveniles, mpgr beta expression was increased in both sexes and amhr2 expression was decreased in males, implying persistent effects of developmental progestagen exposure on amh and pgr expression signalling. No effects of LNG on the gonadal or Müllerian duct development were found, implying that the exposure window was not critical with regard to these endpoints. In juveniles, folliculogenesis had initiated and the Müllerian ducts were larger in females than in males. This new knowledge on sexual development in X. tropicalis is useful in the development of early life-stage endpoints for developmental reproductive toxicity.
authors.affiliation: Uppsala University, Department of Organismal Biology, Norbyvägen 18A, 752 36 Uppsala, Sweden. Electronic address: moa.kvarnryd@ebc.uu.se.
authors.forename: Moa
authors.initials: M
authors.lastname: Säfholm
authors.affiliation: Uppsala University, Department of Organismal Biology, Norbyvägen 18A, 752 36 Uppsala, Sweden. Electronic address: erika.jansson@ebc.uu.se.
authors.forename: Erika
authors.initials: E
authors.lastname: Jansson
authors.affiliation: Umeå University, Department of Chemistry, KBC 6A, Linnaeus väg 6, 901 87 Umeå, Sweden. Electronic address: jerker.fick@umu.se.
authors.forename: Jerker
authors.initials: J
authors.lastname: Fick
authors.affiliation: Uppsala University, Department of Organismal Biology, Norbyvägen 18A, 752 36 Uppsala, Sweden. Electronic address: cecilia.berg@ebc.uu.se.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Berg
mesh_terms: D000818:Animals; D054304:Anti-Mullerian Hormone / Q000235:genetics; D001141:Aromatase / Q000235:genetics; D054750:Ecotoxicology / Q000379:methods*; D052244:Endocrine Disruptors / Q000633:toxicity*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D007814:Larva / Q000187:drug effects; D016912:Levonorgestrel / Q000633:toxicity*; D008297:Male; D009095:Mullerian Ducts / Q000187:drug effects / Q000473:pathology; D011980:Receptors, Progesterone / Q000235:genetics; D060753:Water Quality; D014981:Xenopus / Q000502:physiology*; D029867:Xenopus Proteins / Q000235:genetics
chemical_list: D052244:Endocrine Disruptors; D011980:Receptors, Progesterone; D029867:Xenopus Proteins; D016912:Levonorgestrel; D054304:Anti-Mullerian Hormone; D001141:Aromatase
keywords: Amphibians; Endocrine disruption; Müllerian ducts; Progestagens; Sex differentiation; Sexual development; Test system