title: Effects of atrazine on CYP19 gene expression and aromatase activity in testes and on plasma sex steroid concentrations of male African clawed frogs (Xenopus laevis).
abstract: Some investigators have suggested that the triazine herbicide atrazine can cause demasculinization of male amphibians via upregulation of the enzyme aromatase. Male adult African clawed frogs (Xenopus laevis) were exposed to three nominal concentrations of atrazine (1, 25, or 250 microg atrazine/l) for 36 days, and testicular aromatase activity and CYP19 gene expression, as well as concentrations of the plasma sex steroids testosterone (T) and 17beta-estradiol (E2), and gonad size (GSI) were measured. There were no effects on any of the parameters measured, with the exception of plasma T concentrations. Plasma T concentrations in X. laevis exposed to the greatest concentration of atrazine were significantly less (p = 0.034) than those in untreated frogs. Both CYP19 gene expression and aromatase activities were low regardless of treatment, and neither parameter correlated with the other. We conclude that aromatase enzyme activity and gene expression were at basal levels in X. laevis from all treatments, and that the tested concentrations of atrazine did not interfere with steroidogenesis through an aromatase-mediated mechanism of action.
authors.affiliation: Department of Zoology, National Food Safety and Toxicology Center, Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824, USA. heckerm@msu.edu
authors.forename: Markus
authors.initials: M
authors.lastname: Hecker
authors.forename: June-Woo
authors.initials: JW
authors.lastname: Park
authors.forename: Margaret B
authors.initials: MB
authors.lastname: Murphy
authors.forename: Paul D
authors.initials: PD
authors.lastname: Jones
authors.forename: Keith R
authors.initials: KR
authors.lastname: Solomon
authors.forename: Glen
authors.initials: G
authors.lastname: Van Der Kraak
authors.forename: James A
authors.initials: JA
authors.lastname: Carr
authors.forename: Ernest E
authors.initials: EE
authors.lastname: Smith
authors.forename: Louis
authors.initials: L
authors.lastname: du Preez
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Kendall
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism*; D001280:Atrazine / Q000633:toxicity*; D004958:Estradiol / Q000097:blood; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006540:Herbicides / Q000633:toxicity*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D013737:Testis / Q000187:drug effects* / Q000201:enzymology; D013739:Testosterone / Q000097:blood; D014982:Xenopus laevis
chemical_list: D006540:Herbicides; D012333:RNA, Messenger; D013739:Testosterone; D004958:Estradiol; D001141:Aromatase; D001280:Atrazine