Interspecies Scaling of the Bioaccumulation of Lipophilic Xenobiotics in Fish: an Example Using Trifluralin

A poorly understood factor that may influence differences in the accumulation of a xenobiotic among fishes is interspecies differences in physiology. We have extensively studied the uptake, distribution, and excretion kinetics of the lipophilic herbicide trifluralin (TF) in fish, using a static water exposure system and compartmental toxicokinetic models. We obtained quantitative estimates of physiologically based toxicokinetic parameters such as uptake clearance, apparent volume of distribution, and elimination clearance due to xenobiotic metabolism, in rainbow trout, channel catfish, and bluegill sunfish at two acclimation temperatures. In these and other species (largemouth bass, gizzard shad, fathead minnows, and lake sturgeon), oxygen consumption rate, total lipid content, plasma protein binding, and in vitro biotransformation rates from liver homogenates were determined and examined for their capacities to predict toxicokinetic parameter values. The uptake clearance of TF was predictable based on the oxygen consumption rate, and in vitro TF biotransformation rate was a useful predictor of the in vivo metabolic clearance of TF. Lipid content, however, did not predict the apparent volume of distribution of TF. Values of uptake and metabolism clearance were predicted in largemouth bass, gizzard shad, fathead minnows, and lake sturgeon, using the oxygen consumption and the in vitro TF biotransformation rates. These predicted parameters were then used to successfully simulate the toxicokinetics of TF in these species. Keywords—Interspecies Scaling Bioconcentration Biotransformation Trifluralin