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Evaluating the biotic ligand model for toxicity and the alleviation of toxicity in terms of cell membrane surface potential
Author(s) -
Wang Peng,
Zhou DongMei,
Li LianZhen,
Luo XiaoSan
Publication year - 2010
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.186
Subject(s) - biotic ligand model , ligand (biochemistry) , metal toxicity , toxicity , metal , chemistry , biophysics , membrane , membrane potential , ionic bonding , metal ions in aqueous solution , environmental chemistry , ion , biology , biochemistry , receptor , organic chemistry
The electrostatic nature of plant cell membrane (CM) plays significant roles in ionic interactions at the CM surface and hence in the biotic effects of metal ions. Increases in major cations (commonly Ca 2+ , Mg 2+ , H + , Na + , K + , etc.) in bulk‐phase medium reduce the negativity of CM surface electrical potential (ψ 0 ), but these slightly increase the driving force of a metal ion crossing CMs (surface‐to‐surface transmembrane potential difference, E m,surf ). Toxicologists commonly attributes the interactions between heavy metals and common cations (e.g., H + , Ca 2+ , and Mg 2+ ) to competitions for binding sites at a hypothetical CM surface ligand. The ψ 0 effects are likely to be more important to metal toxicity and the alleviation of toxicity than site‐specific competition. Models that do not consider ψ 0 , such as the biotic ligand model (BLM) and the free ion activity model (FIAM), as usually employed are likely to lead to false conclusions about competition for binding at CM surface ligands. In the present study a model incorporating ψ 0 effects and site‐specific competition effects was developed to evaluate metal (Cu 2+ , Co 2+ , and Ni 2+ ) toxicities threshold (EA50, causing 50% inhibition) for higher plants. In addition, the mechanisms for the effects of common cations on toxicity of metals were also explored in terms of CM surface electrical potential. Environ. Toxicol. Chem. 2010;29:1503–1511. © 2010 SETAC