Methyl mercury toxicokinetics in channel catfish (Ictalurus punctatus) and largemouth bass (Micropterus salmoides) after intravascular administration. Environ Toxicol Chem 16:990–996

Abstract—We compared the differences in the distribution and elimination of CH3Hg after intraarterial injection and serial blood removal in catfish and bass of similar body size under consistent water quality conditions. The blood and plasma concentration– time profiles of individual fish were analyzed using a three-compartment, clearance–volume model. The plasma protein binding of CH3Hg was determined by ultrafiltration (30,000 mol. wt. cutoff) and the binding affinity (r) of CH3Hg for red blood cells (RBCs) was also calculated. Toxicokinetic analysis of the plasma concentration–time profiles provided the following values: apparent volume of distribution at steady state (Vss) 5 30 6 14 ml/g (catfish), 6.2 6 2 ml/g (bass); total body clearance (Clb) 5 0.026 6 0.011 ml/h/g (catfish), 0.0057 6 0.001 ml/h/g (bass). The values of Vss and Clb estimated from the blood concentration–time profiles in catfish and bass were fivefold lower. The elimination half-life from blood and plasma was between 814 and 1670 h and was not statistically different between species or reference fluid. The AUC0→ ` for blood was over three times higher than plasma, due to the binding of CH3Hg to RBCs. The unbound fraction of CH3Hg in bass plasma was 14-fold lower (0.25 vs. 3.64%) and the r for RBCs was 20 times greater than catfish (5,974 vs. 289). The decreased binding to plasma and RBCs in catfish is consistent with the increased extravascular distribution and clearance capacity of CH3Hg in catfish because a larger fraction of the CH3Hg in blood is available to distribute outside the vascular system. Keywords—Methyl mercury Toxicokinetics Catfish Bass Plasma bindin