title: Plasma concentrations of estradiol and testosterone, gonadal aromatase activity and ultrastructure of the testis in Xenopus laevis exposed to estradiol or atrazine.
abstract: The ultrastructure of testicular cells of adult male African clawed frogs (Xenopus laevis) exposed to either estradiol (0.1 microg/L) or 2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine (atrazine; 10 or 100 microg/L) was examined by electron microscopy and compared to plasma concentrations of the steroid hormones, testosterone (T) and estradiol (E2), testicular aromatase activity and gonad growth expressed as the gonado-somatic index (GSI). Exposure to E2 caused significant changes both at the sub-cellular and biochemical levels. Exposure to E2 resulted in significantly fewer sperm cells, inhibition of meiotic division of germ cells, more lipid droplets that are storage compartments for the sex steroid hormone precursor cholesterol, and lesser plasma T concentrations. Although not statistically significant, frogs exposed to E2 had slightly smaller GSI values. These results may be indicative of an inhibition of gonad growth and disrupted germ cell development by E2. Concentrations of E2 in plasma were greater in frogs exposed to E2 in water. Exposure to neither concentration of atrazine caused effects on germ cell development, testicular aromatase activity or plasma hormone concentrations. These results suggest that atrazine does not affect testicular function. In contrast, exposure of male X. laevis to E2 led to sub-cellular events that are indicative of disruption of testicular development, and demasculinization processes (decrease of androgen hormone titers). These results indicate that atrazine does not cause responses that are similar to those caused by exposure to E2.
authors.affiliation: Department of Zoology, Aquatic Toxicology Laboratory, 218C National Food Safety and Toxicology Center, Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, USA. heckerm@msu.edu
authors.forename: Markus
authors.initials: M
authors.lastname: Hecker
authors.forename: Wan Jong
authors.initials: WJ
authors.lastname: Kim
authors.forename: June-Woo
authors.initials: JW
authors.lastname: Park
authors.forename: Margaret B
authors.initials: MB
authors.lastname: Murphy
authors.forename: Daniel
authors.initials: D
authors.lastname: Villeneuve
authors.forename: Katherine K
authors.initials: KK
authors.lastname: Coady
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: D000704:Analysis of Variance; D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D001280:Atrazine / Q000633:toxicity; D004958:Estradiol / Q000097:blood* / Q000633:toxicity; D008297:Male; D008854:Microscopy, Electron; D013094:Spermatozoa / Q000187:drug effects; D013737:Testis / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D013739:Testosterone / Q000097:blood*; D014982:Xenopus laevis / Q000033:anatomy & histology / Q000097:blood*
chemical_list: D013739:Testosterone; D004958:Estradiol; D001141:Aromatase; D001280:Atrazine