Plasma concentrations of estradiol and testosterone, gonadal aromatase activity and ultrastructure of the testis in Xenopus laevis exposed to estradiol or atrazine.
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.
Hecker
Markus
M
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
Kim
Wan Jong
WJ
Park
June-Woo
JW
Murphy
Margaret B
MB
Villeneuve
Daniel
D
Coady
Katherine K
KK
Jones
Paul D
PD
Solomon
Keith R
KR
Van Der Kraak
Glen
G
Carr
James A
JA
Smith
Ernest E
EE
du Preez
Louis
L
Kendall
Ronald J
RJ
Giesy
John P
JP
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*
D013739:Testosterone; D004958:Estradiol; D001141:Aromatase; D001280:Atrazine