PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P559) Endocrine Disruptor Gene and Protein Biomarkers: Differential Expressions in Nonylphenol and Estradiol-17b Treated Trout.

Arukwe, Augustine^*,1, ¹ University of Windsor, Great lakes Institute, Windsor, Ontario, Canada

ABSTRACT- The time- and dose-dependent transcriptional and translational expression of biomarker genes and proteins in nonylphenol(NP)- and estradiol-17b(E2)-treated juvenile rainbow trout is studied. Fish were exposed to nonylphenol (1, 5 and 25 mg/kg) and estradiol (5 mg/kg) and sacrified at 2, 6, 12, 24, 48 and 72 h after exposure. The estrogen receptor (ER), vitellogenin (Vtg) and eggshell zona radiata protein (Zr-protein) gene expressions were analyzed in total liver RNA using Northern and slot hybridization with specific cDNA probes. Plasma Vtg and Zr-protein levels were evaluated using indirect ELISA. While Zr-protein gene showed an induction only at 24h post-exposure, the plasma protein levels showed a time-dependent increase in the 25mg NP treated group. Vtg transcripts showed an apparent time-dependent increase without a concomitant increase in protein levels in the 25mg NP treated fish. Time-dependent increases in Vtg and Zr-protein gene expressions without the corresponding increases in ER gene transcription was observed in E2-treated fish at 2, 6 and 12h post-exposure. Induction of ER gene transcripts was observed from 24 h and did not change significantly at 48 and 72h. In the E2-treated fish, induction of plasma Vtg levels was observed at 48 and 72h, while plasma Zr-protein was induced at 24, 48 and 72h, after exposure. We conclude that the E2- and NP-induced Vtg and Zr-protein gene expressions at the early time intervals after exposure are not dependent on increase in the transcriptional activity of the ER gene and that Vtg and Zr-protein gene transcriptions require only basal or minimal ER concentration, in addition to other mechanisms.

Key words: Endocrine disruptors, Biomarkers, Differential expressions, Rainbow trout