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EVALUATION OF EFFECTS OF THE SYNTHETIC ANDROGEN METHYLTESTOSTERONE ON REPRODUCTION IN THE FATHEAD MINNOW
Citation:
Korte, J J., M D. Kahl, K M. Jensen, AND G T. Ankley. EVALUATION OF EFFECTS OF THE SYNTHETIC ANDROGEN METHYLTESTOSTERONE ON REPRODUCTION IN THE FATHEAD MINNOW. Presented at 16th Annual Sigma Xi Scientific Poster Exhibition, Univ. of Minnesota-Duluth, Duluth, MN, Feb. 21-25, 2000.
Description:
Various studies have assessed the effects of estrogenic xenobiotics on reproduction and related endpoints in fish. Comparatively less research has been done with chemicals that elicit toxicity through alterations in androgen-mediated processes. The purpose of this study was to evaluate the effects of the potent synthetic androgen, methyltestosterone, on a number of endpoints in reproductively-mature fathead minnows (Pimephales promelas). The protocol used for these experiments was consistent with that proposed by EPA as a Tier 1 screen for potential endocrine disrupting chemicals (EDCs). Exposures were conducted with actively-spawning adults for 21 d, during which secondary sexual characteristics, reproductive behavior, fecundity and F1 viability were assessed. At conclusion of the assay, serum vitellogenin and sex steroid concentrations were determined, and gonadal development assessed via histopathology and measurement of the gonadal somatic index. Tests were conducting a saturator column technology that generated a stock solution of the steriod at or slightly below water solubility, in the absence of a carrier solvent. Fish were exposed to levels of methyltestosterone determined to be sublethal in a 14-d range-finding assay. Water concentrations during the 21-d assay were routinely monitored through the use of a novel radioimmunoassay technique which provided excellent sensitivity for detection of the steriod. Results of these experiments can be used as a basis for evaluating the performance of the 21-d fathead minnow screening assay as a screen for EDCs, and also provide background information for assessing the potential ecological risk of chemicals with this mechanism of action in fish.