PM15 Biomarkers
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(PM230) Lipid peroxides determination in oyster (Crassostrea rhizophorae) and barnacle (Balanus improvisus) using the FOX assay.

Zanette, J1, Monserrat, J1, Bianchini, A1, 1 Fundação Universidade Federal do Rio Grande, Rio Grande, RS, Brazil

ABSTRACT- Oxidative stress leads to membrane PUFA peroxidation, which can induce cell dysfunction. Thus, increments in lipid peroxide levels have been employed as a pollution biomarker of celular damage in aquatic organisms. The present study evaluated the adequacy of FOX (ferrous oxidation/xylenol orange) assay to measure lipid peroxidation (LPO) in mangrove oyster (Crassostrea rhizophorae) gills and barnacle (Balanus improvisus) whole body. Supernatant from tissue extracts were obtained by centrifugation (1,000 x g; 10 min; 4oC) after homogenization in methanol 100%. Adequate reaction time was selected when absorbance (550 nm) reached a plateau. Different sample volumes were tested (oyster = 5, 10, 20 and 40 L with 1:9 dilution; barnacle = 2.5, 5, 10, 20 L with 1:49 dilution and 10, 20 and 30 L with 1:9 dilution). Lipid peroxides content was expressed as cumene hidroperoxide (CHP) equivalents. After the reaction time, CHP was added to both reaction blanks and samples to determine unspecific difference between blank plus CHP and samples plus CHP. In such case, a correction factor (CF) was calculated for each sample. In oysters, CF higher than 1.3 showed a positive correlation with the calculated LPO values, thus causing an abnormal increase in these values. In barnacles, CF higher than 1.9 showed a negative correlation with the calculated LPO values, thus causing an abnormal decrease in these values. Our results indicate that the unspecific difference between blanks plus CHP and samples plus CHP, i.e., different CFs, could induce to important and variable biases in LPO determination by FOX-assay in different animal groups. (This work is part of RECOS project - Institutos do Milênio - Brazilian Ministry of Science and Technology)

Key words: lipid peroxidation, FOX assay, Crassostrea rhizophorae, Balanus improvisus

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