Modeling zinc regulation in small mammals

Abstract

Due to large zinc discharges into the global environment, both terrestrial and aquatic environments have been polluted with zinc. The embanked floodplains of the lower Rhine River in the Netherlands contain large amounts of heavy metals, including zinc. These large amounts of heavy metals may pose risks to flora and fauna by accumulation in food webs, and risk assessment may be required. However, toxicokinetic models for zinc metabolism in mammalian wildlife species are currently lacking. The present study describes the development of a zinc kinetics model that predicts internal zinc concentrations in small mammals by modeling zinc absorption and excretion dependent on the dietary zinc intake using adapted Michaelis-Menten equations. The equations were parameterized based on experimental data reported in the scientific literature. Within the dietary zinc range of 3 to 104 mg/kg dry weight, the model predicts internal zinc concentrations and shows that the internal zinc is regulated within this range. Outside this range, the model could not be calibrated due to a lack of data. Validation of the model with four small mammal species living in an embanked floodplain along a distributary of the Rhine River illustrated that the model predicts internal zinc concentrations differing up to a factor of 1.6 (Common shrew) to 1.7 (Common vole) from field measurements.

Spatially Explicit Analysis of Metal Transfer to Biota: Influence of Soil Contamination and Landscape

“…Thus, if total concentrations in soils are better estimates of the contamination of the diet than extractable ones, this may explain why we found here better correlations between internal TMs and soil TMs using total rather than extractable concentrations. The slight increase in hepatic Zn concentrations in small mammals along the pollution gradient is consistent with previous studies, which have provided evidence for slight differences between polluted and control field sites and the ability of small mammals to regulate internal levels of this essential element [7], [34], [69], [79], [80].…”