W3 AM Toxicogenomics in Environmental Studies
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(DEN-1117-862896) Dietary exposure of largemouth bass to OCPs changes gene expression throughout the reproductive cycle.

Reyero, N¹, Barber, D¹, Johnson, K², Sepúlveda, M³, Gross, T^{1, 2}, Denslow, N¹, ¹ University of Florida, Gainesville, FL, USA² USGS-Center for Aquatic Resource Studies, Gainesville, FL, USA³ Purdue University, West Lafayette, IN, USA

ABSTRACT- Largemouth bass were exposed subchronically through the diet to either p,p DDE (7, 37 and 185 ppm) or dieldrin (0.6 and 3 ppm) for up to four months during their prime reproductive season. Our aim was to investigate the temporal expression patterns of several genes important for reproduction, including the three estrogen receptors (ERs), androgen receptor (AR), vitellogenin (Vtg), StAR, Cyp1A, Cyp2, Cyp3A and aromatase, among others. We also wanted to compare how different doses of p,p DDE and dieldrin would affect the expression pattern of these genes. The gene expression was measured and quantified by real-time PCR, and plasma E2 and 11KT concentrations by RIA. The predominantly expressed ER isotypes in the liver were ERs alpha and beta2, however, only ER alpha levels changed significantly over time, increasing highly during the reproductive season, in consonance with the levels of Vtg and E2. The levels of ER beta2 remain relatively constant through this time frame in the liver. ER beta1 is the least expressed isotype in the liver, but its expression peaks with the highest plasma E2 value. The expression patterns of the three ERs in gonad were distinct from the liver profile. In the gonad, ERs beta 1 and 2 are highly expressed early in the cycle and appear to be repressed with increasing plasma E2 levels. ER alpha is the least expressed. Exposure to p,&ptilde;DDE increased ER alpha and Vtg in the liver of both males and females, however dieldrin had no effect on these genes in males but did increase Vtg in females. In addition, there was a marked increase in Cyp3A, suggesting the fact that metabolism of endogenous hormones was increased. Our data shows that p,p DDE is acting mostly as a weak estrogen mimic and dieldrin affects mainly metabolism and detoxification pathways.

Key words: gene arrays, DDE, dieldrin, ER