title: Tebuconazole disrupts steroidogenesis in Xenopus laevis.
abstract: A 27-day controlled exposure study of adult male African clawed frogs (Xenopus laevis) was conducted to examine the mechanism by which tebuconazole may disrupt steroidogenesis. The fungicide was measured by LC-MS/MS in tank water and in target tissues (adipose, kidney, liver, and brain), and we observed tissue-specific bioconcentration with BCF up to 238. Up to 10 different steroid hormones were quantified in gonads using LC-MS/MS and in plasma using GC-MS/MS and a radioimmunoassay was performed for further measurement of androgens. In order to assess whether effects increased with exposure or animals adapted to the xenobiotic, blood samples were collected 12 days into the study and at termination (day 27). After 12 days of exposure to 100 and 500μgL(-1) tebuconazole, plasma levels of testosterone (T) and dihydrotestosterone (DHT) were increased, while plasma 17β-estradiol (E2) concentrations were greatly reduced. Exposure to 0.1μgL(-1), on the other hand, resulted in decreased levels of T and DHT, with no effects observed for E2. After 27 days of exposure, effects were no longer observed in circulating androgen levels while the suppressive effect on E2 persisted in the two high-exposure groups (100 and 500μgL(-1)). Furthermore, tebuconazole increased gonadal concentrations of T and DHT as well as expression of the enzyme CYP17 (500μgL(-1), 27 days). These results suggest that tebuconazole exposure may supress the action of CYP17 at the lowest exposure (0.1μgL(-1)), while CYP19 suppression dominates at higher exposure concentrations (increased androgens and decreased E2). Increased androgen levels in plasma half-way into the study and in gonads at termination may thus be explained by compensatory mechanisms, mediated through increased enzymatic expression, as prolonged exposure had no effect on circulating androgen levels.
authors.affiliation: Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA; Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: rikkesemail@gmail.com.
authors.forename: Rikke
authors.initials: R
authors.lastname: Poulsen
authors.affiliation: Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Xuan
authors.initials: X
authors.lastname: Luong
authors.affiliation: Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA; Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA; Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Hansen
authors.affiliation: Toxicology Laboratory, Section of Advanced Drug Analysis, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Bjarne
authors.initials: B
authors.lastname: Styrishave
authors.affiliation: Laboratory for Integrative Studies in Amphibian Biology, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA. Electronic address: tyrone@berkeley.edu.
authors.forename: Tyrone
authors.initials: T
authors.lastname: Hayes
mesh_terms: D000728:Androgens / Q000378:metabolism; D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism; D013196:Dihydrotestosterone / Q000378:metabolism; D004958:Estradiol / Q000097:blood / Q000235:genetics / Q000378:metabolism; D005659:Fungicides, Industrial / Q000633:toxicity; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D006066:Gonads / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008297:Male; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D013739:Testosterone / Q000378:metabolism; D014230:Triazoles / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D000728:Androgens; D005659:Fungicides, Industrial; D014230:Triazoles; D014874:Water Pollutants, Chemical; D013196:Dihydrotestosterone; D013739:Testosterone; C087114:tebuconazole; D004958:Estradiol; D001141:Aromatase; D013254:Steroid 17-alpha-Hydroxylase
keywords: Androgens; Bioconcentration; Compensatory responses; Endocrine disruptor; Fungicide