ACETYLCHOLINESTERASE, AN OLD BIOMARKER WITH A NEW FUTURE - FIELD TRIALS IN ASSOCIATION WITH 2 URBAN RIVERS AND A PAPER-MILL IN NEWFOUNDLAND

Biological markers are sensitive, cost effective tools for identifying risks of environmental contamination, The cytochrome P450-linked mixe d-function oxygenase (MFO) system has been extensively validated in th e environment, not only in association with point sources of pollution , but also in association with contamination over broad geographical a reas, However, there is a recognized need for the establishment of bio markers for assessing a variety of toxicological endpoints. With respe ct to neuromuscular functions, a recent study in the North Sea has ind icated that the 'old' biomarker, acetylcholinesterase (ACHE), which is sensitive to selected organophosphate and carbamate pesticides, may b e responding to low levels of contaminants in the environment, putativ ely by compounds other than, or in addition to, pesticides. We now pro vide evidence for such a possibility. A distinct depression of ACHE wa s found in muscle tissues of trout (Salmo trutta) taken from two urban rivers in St. John's (Virginia River and Rennie's Mill River), in com parison with a nearby reference river (South Brook). Most striking was the fact that depression was observed in the 50% range. A similar hig h level of enzyme depression was observed in muscle tissues of flounde r (Pleuronectes americanus) taken in the area of a pulp and paper mill (Birchy Bay in the Bay of Islands), in comparison with a nearby refer ence site. Depression of ACHE was associated with induction of MFO enz yme activity (ethoxyresorufin-O-deethylase) in liver tissues of both t rout and flounder. We provide evidence and discussion that contaminant s other than pesticides, including compounds in complex mixtures of co mbustion hydrocarbons and natural wood leachate, could be responsible for the depressed ACHE levels observed in our studies (as well as thos e in the North Sea) and suggest that this old biomarker may have a new future in biological monitoring and assessment programmes.