M4 AM Endocrine Disruption in Fish
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 4

(ARU-1117-722946) Modulation of the StAR protein and P450scc in the brain of juvenile Atlantic salmon (Salmo salar) is a novel aspect of nonylphenol toxicity.

Arukwe, A.¹, ¹ Department of Biology, Norwegian Univ. of Sci. & Technol. (NTNU), Trondheim, NORWAY

ABSTRACT- Gene expression patterns for key brain steroidogenic (StAR, P450scc, CYP11), xenobiotoc- and steroid-metabolizing enzymes (CYP1A1 and CYP3A) have been investigated in waterborne nonylphenol (NP; 5, 15 and 50 g/L) treated juvenile Atlantic salmon (Salmo salar), in addition to control and vehicle (ethanol control) exposed fish and sampled at different time intervals (0, 3 and 7 days) after exposure. Gene expression patterns were studied using real-time PCR and qualitatively using Northern hybridization. Treatment of juvenile salmon with noylphenol caused significant induction of StAR protein mRNA at day 7 post-exposure in the group receiving 15g NP/L. P450scc was first induced in the group treated with 5g NP/L at day 7, thereafter an apparent nonylphenol-concentration dependent decreases in P450scc mRNA were observed. Exposure to vehicle, ethanol, caused a significant induction of P450scc mRNA at day 3 post-exposure. CYP11 mRNA was significantly induced at day 3 after exposure to 5g NP/L, thereafter CYP11 mRNA levels were inhibited below control levels in the 15 and 50g NP/L groups at day 3. At day 7, significant induction of CYP11 mRNA was observed only in the group exposed to 15g NP/L. For CYP1A1 mRNA, an apparent nonylphenol concentration-dependent decreases were observed at day 7 post-exposure. CYP3A mRNA was significantly induced by all exposure concentrations at day 7. When exposed groups were compared, CYP3A transcript was significantly induced between 5 and 15g NP/L, and decreased between 15 and 50g NP/L. The ethanol control showed a significant reduction of CYP3A mRNA at day 3 post-exposure. The present study has demonstrated variations in three key steroidogenic proteins, xenobiotic and steroid metabolizing cytochrome P450 isozyme levels in the brain of nonylphenol exposed juvenile salmon. Thus representing a novel aspect of neuroendocrine effects of nonylphenol in fish that need to be studied in more detail.

Key words: StAR, P450scc, Steroidogenesis, Steroid metabolism