FISH HEPATIC MICRONUCLEI AS AN INDICATION OF EXPOSURE TO GENOTOXIC ENVIRONMENTAL CONTAMINANTS

An In vivo assay protocol for detecting hepatic micronuclei in fish wa s performed to evaluate whether this genotoxic response could serve as a bioindicator of environmental exposure to genotoxic substances. The incidence of hepatic micronuclei was compared in brown bullheads (Ame iurus nebulosus) with external lesions collected from a contaminated s ite and fish showing no externally visible pathologies collected from reference sites. Laboratory experiments were performed by exposing hat chery-raised rainbow trout (Onchorhynchus mykiss) to a pulp mill efflu ent extract (XAD-4-NaOH) with known genotoxic activity. Both bullhead and trout were injected with allyl formate to induce hepatic necrosis and regenerative proliferation of hepatocytes prior to examining the l iver tissue for micronuclei. An elevated incidence of hepatic micronuc lei was observed in Hamilton Harbour bullheads showing visible lesions relative to the micronucleus incidence in bullheads from reference si tes with no external pathologies. Similarly, rainbow trout exposed to pulp mill effluent extracts exhibited an elevated incidence of hepatic micronuclei compared to controls. These results suggest that the hepa tic micronucleus assay could serve as a valuable biomonitoring tool fo r assessing the impacts of genotoxic environmental contaminants on fis h. (C) 1997 by John Wiley & Sons, Inc.