BIOMONITORING OF AQUATIC POLLUTION WITH FERAL EEL (ANGUILLA-ANGUILLA).2. BIOMARKERS - POLLUTION-INDUCED BIOCHEMICAL RESPONSES

The primary aim of this study was to select a set of relevant biomarke rs in feral eel for the biological assessment of inland water pollutio n. A suite of biochemical parameters in eel (hepatic biotransformation enzymes and cofactors, antioxidant enzymes, PAH metabolites, DNA addu cts, serum transaminases) was measured in order to determine their res ponse to xenobiotic compounds in the environment. The results of the a nalyses of organic trace pollutants in sediments and eel from six Amst erdam freshwater sites with different pollution levels have been discu ssed in the first part of this paper (Van der Oost, R., Opperhuizen, A ., Satumalay, K., Heida, H. and Vermeulen, N.P.E., 1996a. Biomonitorin g aquatic pollution with feral eel (Anguilla anguilla): I. Bioaccumula tion: biota-sediment ratios of PCBs, OCPs, PCDDs and PCDFs. Aquat. Tox icol., 35: 21-46). The main conclusions drawn from the trends found fo r the levels and activities of biochemical parameters in eel were the following: the phase I biotransformation enzymes in eel liver appeared to be the most sensitive to environmental xenobiotics. Cytochrome b(5 ) (Cyt b(5)), cytochrome P450 1A (CYP1A), ethoxyresurofin-O-deethylase (EROD) and EROD turnover (EROD/P450) in eel liver showed significant responses to contamination, and can therefore be used as biomarkers. L evels of a CYP3A-like protein were significantly elevated in eel from three moderately polluted sires, but since this protein was not induce d in eel from the most polluted site its relevance as a biomarker rema ins unclear. Phase II enzymes and cofactors in eel liver were less sus ceptible to pollutants than phase I enzymes. The activity of UDP glucu ronyl transferase (UDPCT) in eel may, however, be a useful biomarker, while glutathione S-transferase (CST) activity and levels of oxidized glutathione (GSSG) were less sensitive. The reduced glutathione (GSH) cofactor levels in eel liver are most probably not reliable as biomark ers. Hepatic activities of antioxidant enzymes (superoxide dismutase ( SOD), catalase (CAT) and GSH-peroxidase (GPOX)) in eel did not show an y response to pollution and are therefore not feasible as biomarkers. The level of 1-hydroxypyrene (1-OH pyrene) in eel bile might be a usef ul biomarker to determine short-term PAH exposure. The hepatic level o f DNA adducts in eel liver seems to be a sensitive biomarker for expos ure to (and possible effects of) mutagenic and carcinogenic xenobiotic s. In feral eel, serum transaminases are not usable as biomarkers of c hronic intoxication. The proposed set of the most relevant biomarkers for the assessment of inland water pollution with feral eel thus consi sts of the following six parameters: cyt b(5), CYP1A, EROD, EROD/P450, UDPGT and DNA adducts.