CYPS MOLECULAR BIOMARKERS IN RAINBOW TROUT Oncorhynchus mykiss TO ASSESS OIL CONTAMINATION IN A PATAGONIAN STREAM

ABSTRACT Cytochrome P450 (CYP) gene expressions were studied by semi-quantitative polymerase chain reaction (PCR) to assess oil pollution using liver and gills of juvenile rainbow trout Oncorhynchus mykiss sampled from La Mina stream (Bariloche, Argentina), up and downstream of a discharge of petroleum spill from an unproductive wellbore. Data was complemented with laboratory exposure to water accommodated fraction (WAF) from the oil spill. Oil exposure induced gill and liver CYP1A transcription (1.2-1.4-fold), which was used as reference biomarker. In both organs, CYP2K1 transcript was induced after 5 % WAF exposure, 24 h (1.8-2.0-fold), and it was down-regulated in more extended time (1.2-1.5-fold). CYP2M1 transcript levels were down-regulated in liver of impacted wild trout and in trout exposed to 5 % WAF during 96 h (1.5-1.7-fold). CYP2K1 and CYP2M1 are involved in the metabolism of fatty acids and estrogenic hormones, and its down-regulation would indicate metabolic alterations. CYP3A27 levels were only induced in liver of wild trout (1.6-fold), possibly related to crosstalk between aryl hydrocarbon receptor and pregnane X receptor signaling pathway. While CYP1A mRNA expression appears to be a more robust biomarker for detecting the effects of crude oil under different dose and exposure time, the expression of CYP2K1, CYP2M1 and CYP3A27 mRNAs would indicate different time exposure to oil pollution, particularly under high oil concentration in water. Hence, patterns of multiple CYP genes expression in rainbow trout gills and liver could be especially valuable for monitoring programs of crude oil pollution and remediation actions on Patagonian freshwater ecosystems.