Toxicokinetics of waterborne pyrene in rainbow trout (Oncorhynchus mykiss) following branchial or dermal exposure

The uptake and depuration of waterborne pyrene were studied in rainbow trout (Oncorhynchus mykiss) implanted with a dorsal aortic cannula. The trout were placed individually either in an exposure chamber (chamber-restrained mode) or in a 30-1 glass aquarium (free-swimming mode) and exposed to water containing 8 mg l(-1) pyrene for 4 h at 12+/-2 degrees C. The exposure chamber could be divided by a latex diaphragm into the front and the rear subcompartments and used to study either the branchial or the dermal uptake of waterborne pyrene by trout. After pyrene exposure, the trout were provided with uncontaminated water to study the depuration of pyrene. Blood samples were withdrawn through the cannula at specific time intervals during and after pyrene exposure. The blood samples were extracted by hexane and analyzed for pyrene by HPLC. Pyrene concentrations in the blood of trout after branchial exposure were significantly higher than those of the dermally exposed trout indicating the gills as the most important route of waterborne pyrene absorption. Our results also showed that the chamber-restrained trout had a significantly larger area under the blood concentration-time curve than the free-swimming trout although both groups of fish had been exposed to 8 mg l(-1) of waterborne pyrene. Since an exposure chamber may enhance the systemic absorption of waterborne pyrene by the trout, care must be exercised in extrapolating results from the chamber-restrained trout to the free-swimming trout.