title: Does atrazine affect larval development and sexual differentiation of South African clawed frogs?
abstract: The potential impact of atrazine (ATZ) on gonadal malformations in larval Xenopus laevis has been controversially discussed, and a hypothesis has been generated that ATZ might induce the estrogen-synthesizing enzyme aromatase, leading to feminization or demasculinization. Recently, extensive long-term studies clearly indicate that no adverse effect of ATZ on larval development and sexual differentiation could be found. Therefore, to determine potential transient impacts of ATZ on sexual differentiation processes, short-term exposures were conducted using tadpoles treated for 4 days with ATZ at 25 microg/L. The expression levels of the key players for sexual differentiation in amphibians were determined in the brain, assessing aromatase, 5alpha-reductase type 1 (S1) and type 2 (S2), and the gonadotropins luteinizing hormone and follicle-stimulating hormone, and in the gonads, measuring aromatase, S1, and S2, by means of quantitative RT-PCR. No significant changes in any of these parameters have been found, implicating, in accordance with recent long-term exposures, that no aromatase induction by ATZ could be observed, and it seems likely that no further endocrine mechanism of ATZ affecting sexual differentiation in X. laevis exists.
authors.affiliation: Department of Aquaculture and Ecophysiology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany. werner.kloas@igb-berlin.de
authors.forename: Werner
authors.initials: W
authors.lastname: Kloas
authors.forename: Ilka
authors.initials: I
authors.lastname: Lutz
authors.forename: Ralph
authors.initials: R
authors.lastname: Urbatzka
authors.forename: Tim
authors.initials: T
authors.lastname: Springer
authors.forename: Hank
authors.initials: H
authors.lastname: Krueger
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Wolf
authors.forename: Larry
authors.initials: L
authors.lastname: Holden
authors.forename: Alan
authors.initials: A
authors.lastname: Hosmer
mesh_terms: D000818:Animals; D001280:Atrazine / Q000494:pharmacology*; D001921:Brain / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers / Q000235:genetics; D006066:Gonads / Q000378:metabolism; D007814:Larva / Q000187:drug effects; D008297:Male; D012733:Sex Differentiation / Q000187:drug effects*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism*
chemical_list: D005819:Genetic Markers; D001280:Atrazine