TOXICOKINETICS OF TRIFLURALIN IN RAINBOW-TROUT

Rainbow trout weighing 80 g were statically exposed at 12-degrees-C to 2 ng/ml C-14-trifluralin (TF), a widely used herbicide. After various exposure times, TF was determined in exposure water, plasma, and carcass homogenate; the total amount of metabolites formed was also estimated. A two compartment toxicokinetic model, that included gill plasma flow and the plasma/water distribution coefficient as model parameters, was used to analyze these concentration-time profiles. The value of the uptake clearance (33.3 ml.h-1.g-1) approximated the ventilation volume of the gills, an indication that TF uptake was water flow limited. The apparent volume of distribution was 3,240 ml/g. The model predicted BCF and depuration half-life were 2280 and 144 h. Five trout weighing between 238 and 1339 g received 1 mg/kg TF via intraaortic injection. The plasma concentration-time profile was characterized up to 240 h and analyzed using a three compartment model. TF distributed rapidly and extensively to tissues; its elimination half-life was variable, ranging from 54 to 290 h in three of the fish. In two fish, the plasma concentration time profile showed no detectable decline between 50 and 240 h. A free fraction in plasma for TF of 0.39% was determined by equilibrium dialysis. Pretreatment of hepatic microsomes with TF in vitro and exposure of fish to TF in vivo prior to microsome preparation did not affect N-depropylase activity.