Exposure‐related patterns of biochemical indicators in rainbow trout exposed to no. 2 fuel oil

Abstract

AbstractSeveral biochemical indicators were evaluated as monitoring techniques in rainbow trout (Oncorhynchus mykiss) exposed to No. 2 fuel oil (2FO) for their ability to predict the exposure concentration. The principal factor affecting the response of the ratio of liver weight to body weight, microsomal and cytosolic protein, reduced glutathione (GSH), 7‐ethoxyresorufin O‐deethylation (EROD) and metallothionein (MTN) was the length of exposure, not the exposure concentration. Two patterns of response were observed, depending on the length of exposure. In rainbow trout exposed for 3 d to 12 to 100 mg/L 2FO, cytoplasmic protein and EROD activity were elevated and GSH was depleted; in fish exposed for 21 d, liver size, microsomal and cytoplasmic protein, EROD activity, GSH and MTN were all increased. The appearance of an MTN response due to 2FO exposure causes us to question the use of this protein as a metal bioindicator. Furthermore, we did not observe a dose‐dependent response in any of the biochemical responses and suggest that toxicity was responsible for the lack of concentration dependence. This lack of a concentration‐dependent response will complicate the use of these biochemical indicators in a biomonitoring program.