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() Molecular, Protein and Histological Indicators in Fathead Minnow and Pearl Dace Exposed to EE2 in a Whole Lake Dosing Experiment .

Lazorchak, J.1, Palace, V.2, Evans, R.2, Wautier, K.2, Flick, R.1, Wiechman, B.3, Braam, A3, Kidd, K.4, Lattier, D.1, 1 U.S. EPA, Cincinnati, OH, USA2 Freshwater Institute, Winnipeg, Manatoba, Canada3 PAI c/o U.S. EPA, Cincinnati, OH, USA4 University of New Brunswick, Saint John, New Brunswick, Canada

ABSTRACT- A whole-lake endocrine disruption experiment was conducted by Fisheries and Oceans Canada (DFO) at the Experimental Lakes Area (ELA), northwestern Ontario from 2001 to 2003. This experiment examined population, organism, biochemical and cellular-level effects in lake trout, white sucker, fathead minnow, and pearl dace exposed to environmentally-relevant (4-6 ng/L) concentrations of the synthetic estrogen, ethynylestradiol (EE2). The USEPA collaborated in this study by evaluating vitellogenin (Vg) gene expression in male fathead minnow and pearl dace livers from indigenous fish collected from dosed and reference lakes. In addition, from the same collections of fathead minnows and pearl dace, the DFO measured concentrations of vitellogenin protein (Vtg) from whole body homogenates using an indirect competitive ELISA assay and performed histological analyses on liver and gonads. Gene expression results indicated that male fathead minnows and pearl dace showed induced Vg levels throughout the dosing season and females of both fish showed increased levels of gene expression beyond the normal breeding season. Vtg protein levels were significantly elevated over background levels and over those fish collected from control lakes. Histological sections of fathead minnow testes from Lake 260 revealed widespread fibrosis and inhibited development. In addition, EE2-exposed fish had kidney anomalies including edema within and between the kidney tubules, and hyaline deposits in the tubule cells. Liver tissues from fish from Lake 260 also had reduced glycogen stores and increased liver cell size when compared to baseline data from the same lake and reference lake fish.

Key words: gene expression, ethynylestradiol, protein, histology

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