You are here:
A Physiologically Based Model for Methylmercury in Female American Kestrels
Citation:
NICHOLS, J. W., R. S. BENNETT, R. ROSSMANN, J. B. FRENCH, AND K. G. SAPPINGTON. A Physiologically Based Model for Methylmercury in Female American Kestrels. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 29(8):1854-1867, (2010).
Impact/Purpose:
A physiologically based toxicokinetic (PBTK) model was developed to describe the uptake, distribution, and elimination of methylmercury (CH3Hg) in female American kestrels
Description:
A physiologically based toxicokinetic (PBTK) model was developed to describe the uptake, distribution, and elimination of methylmercury (CH3Hg) in female American kestrels. The model consists of six tissue compartments corresponding to the brain, liver, kidney, gut, red blood cells, and remaining carcass. Additional compartments describe the elimination of CH3Hg to eggs and growing feathers. Dietary uptake of CH3Hg among compartments is mediated by the flow of blood plasma. To the extent possible, model parameters were developed using information from American kestrels. Additional parameters were based on measured values for closely related species and allometric relationships for birds. The model was calibrated using data from dietary dosing studies with American kestrels. Good agreement between model simulations and measured CH3Hg concentrations in blood and tissues was obtained by fitting model parameters that control dietary uptake of CH3Hg. Modeled results suggest that the kinetics of CH3Hg in kestrels become multiexponential when events that eliminate/redistribute CH3Hg (e.g., egg production) occur on a time-scale of hours. The results of this effort are consistent with observed patterns of CH3Hg elimination in birds including the effect of egg laying order and the dominant influence of feather molt. The model can be used to extrapolate CH3Hg kinetics from American kestrels to other bird species by appropriate respecification of parameter values. Alternatively, when combined with a bioenergetics-based description, the model could be used to simulate CH3Hg kinetics in a long-term environmental exposure.