Interspecies-Extrapolated Biotic Ligand Model to Predict Arsenate Toxicity to Terrestrial Plants with Consideration of Cell Membrane Surface Electrical Potential

Arsenic is a metalloid that is highly toxic to living organisms in the environment. In this study, toxicity caused by inorganic arsenate (As(V)) to terrestrial plants, such as barley Hordeum vulgare and wheat Triticum aestivum, was predicted using the existing biotic ligand model (BLM) for bioluminescent Aliivibrio fischeri via interspecies extrapolation. Concurrently, the concept of cell plasma membrane electrical potential (Ψ(0)) was incorporated into the extrapolated BLM to improve the model predictability in the presence of major cations such as Ca(2+). The 50% effective As(V) toxicity (EC(50){HAsO(4)(2−)}) to H. vulgare decreased from 45.1 ± 4.34 to 15.0 ± 2.60 µM as Ca(2+) concentration increased from 0.2 to 20 mM owing to the accumulation of H(2)AsO(4)(−) and HAsO(4)(2−) on the cell membrane surface. The extrapolated BLM, which only considered inherent sensitivity, explained well the alteration of As(V) toxicity to H. vulgare and T. aestivum by Ca(2+) with in an order of magnitude, when considering a linear relationship between Ψ(0) and EC(50){HAsO(4)(2−)}.