HPLC determination of plasma thiocyanate concentrations in fish blood: application to laboratory pharmacokinetic and field-monitoring studies

The pharmacokinetics of thiocyanate (SCN-) in the blood plasma of 35-g rainbow trout (Oncorhynchus mykiss) were followed during a 20-day exposure to 39.8 mg SCN- liter-1 and the subsequent 16-day depuration period. SCN- concentrations were determined by reverse-phase HPLC. Kinetic constants were estimated using a one-compartment first-order kinetic model fitted to the data by the computer programs BIOFAC and SYSTAT. The respective BIOFAC and SYSTAT estimates for the uptake rate constant (k1, 0.55 and 0.49 day-1), the depuration rate constant (k2, 0.34 and 0.29 day-1), and the bioconcentration factor (BCF, 1.61 and 1.66) were similar for both methods of calculation. Field studies were conducted to determine the impact of SCN- on white sucker (Catostomus commersoni) populations in waters receiving SCN(-)-bearing effluents. The assessment was based on SCN- concentrations in water and fish plasma, and the thyroid histology of the fish. Although SCN- was detected in the water at one site, no SCN- was detected in fish plasma and none of the thyroid pathology characteristic of chronic SCN- exposure was present. The results suggest that SCN- was not a hazard to the white sucker populations studied.