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Effects of steroids and dioxin (2,3,7,8-TCDD) on the developing wolffian ducts of the tiger salamander Ambystoma tigrinum.

The present study investigated the effects of the dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on steroid-dependent development of amphibian gonaducts. Sexually undifferentiated larval tiger salamanders (Ambystoma tigrinum), with immature gonads were immersed in a sub lethal solution of technical-grade TCDD and injected with dihydrotestosterone (DHT) or estradiol ([E.sub.2]). Morphometrics were used to analyze the effects and interactions of the sex-steroids and TCDD treatments on wolffian ducts. In sexually differentiated A. tigrinum larvae, growth of this tissue is androgen-dependent and is antagonized by estradiol. We found that in sexually undifferentiated A. tigrinum, mean wolffian duct epithelial area was increased by both steroid treatments. DHT stimulated an increase in the size and number of cells while [E.sub.2] only stimulated an increase in cell size. In the absence of exogenous steroid, TCDD mimicked [E.sub.2] by increasing mean cell size in the wolffian duct. TCDD agonized the stimulatory action of DHT on wolffian duct cell size. TCDD had no effect on wolffian duct epithelium in [E.sub.2]-treated animals. These findings implicate environmental dioxins as potentially important modulators of amphibian reproduction and further validate the utility of urodele gonaducts as a useful bioassay for the detection of endocrine-active environmental compounds.

Alan M. Vajda * and David O. Norris *. Department of EPO Biology, University of Colorado, Boulder.

* Denotes membership in the Colorado-Wyoming Academy of Science.
COPYRIGHT 2002 Colorado-Wyoming Academy of Science
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Author:Vajda, Alan M.; Norris, David O.
Publication:Journal of the Colorado-Wyoming Academy of Science
Article Type:Brief Article
Geographic Code:1USA
Date:Apr 1, 2002
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