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HP5 Biomarkers
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1:20 PM - 5:20 PM, Thursday

() Effects of atrazine exposure on aromatase activity and CYP19 gene expression in male adult Xenopus laevis.

Park, J.-W.¹, Hecker, M.¹, Murphy, M.¹, Jones, P.¹, Solomon, K.², van der Kraak, G.², Kendall, R.³, Giesy, J.¹, ¹ Michigan State University, East Lansing, MI, 48824² University of Guelph, Guelph, Ontario, USA³ Texas Tech University, Lubbock, Texas, USA

ABSTRACT- It has been hypothesized that atrazine (ATZ) affects the endocrine system of male amphibians by up-regulating the enzyme aromatase, the enzyme that transforms testosterone to estradiol. However, there has been no direct prove of this potential mechanism of action. This study was designed to test the hypothesis that ATZ has the potential to interact with either the regulation and/or expression of the aromatase gene or the activity of the aromatase enzyme. Adult male African clawed frogs (Xenopus laevis) were exposed to 0, 0.8 +/- 0.2, 24.6 +/- 4.2 and 258.6 +/- 58.2g/L ATZ, as measured by GC/MS, for 38 days in a static renewal system. After exposure, gonads were analyzed for aromatase activity and expression of the CYP19 gene. There were no significant differences between aromatase activities regardless of treatment. Enzyme activities were similar among the controls (624 +/- 27fmol/h/g tissue; mean +/- SEM), and the two lower treatments (0.8g/L ATZ: 637 +/- 70fmol/h/g tissue; 24.6g/L ATZ: 671 +/- 68fmol/h/g tissue). Although not statistically significant a slight decrease in aromatase activity was observed in the highest exposure group (489.2 +/- 90.8fmol/h/g tissue). Aromatase gene expression in testes, as measured by RT-PCR, was detectable but low when compared to that in females. These results indicate that ATZ is not likely to interact with the endocrine systems of amphibians by altering testicular aromatase activity.

Key words: amphibians, atrazine, aromatase, CYP19