首页> 外文期刊>Environmental Toxicology and Chemistry >PLASMA MEMBRANE SURFACE POTENTIAL (PM) AS A DETERMINANT OF ION BIOAVAILABILITY: A CRITICAL ANALYSIS OF NEW AND PUBLISHED TOXICOLOGICAL STUDIES AND A SIMPLIFIED METHOD FOR THE COMPUTATION OF PLANT PM
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PLASMA MEMBRANE SURFACE POTENTIAL (PM) AS A DETERMINANT OF ION BIOAVAILABILITY: A CRITICAL ANALYSIS OF NEW AND PUBLISHED TOXICOLOGICAL STUDIES AND A SIMPLIFIED METHOD FOR THE COMPUTATION OF PLANT PM

机译:等离子体膜表面电位(PM)决定离子的生物利用度:新的和发表的毒理学研究的临界分析和简化的植物PM的计算方法

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摘要

Plasma membranes (PMs) are negatively charged, and this creates a negative PM surface electrical potential (PM) that is also controlled by the ionic composition of the bathing medium. The PM controls the distribution of ions between the PM surface and the medium so that negative potentials increase the surface activity of cations and decrease the surface activity of anions. All cations reduce the negativity of PM, and these common ions are effective in the following order: Al3+ > H+ > Cu2+ > Ca2+ Mg2+ > Na+ K+. These ions, especially H+, Ca2+, and Mg2+, are known to reduce the uptake and biotic effectiveness of cations and to have the opposite effects on anions. Toxicologists commonly interpret the interactions between toxic cations (commonly metals) and ameliorative cations (commonly H+, Ca2+, and Mg2+) as competitions for binding sites at a PM surface ligand. The PM is rarely considered in this biotic ligand model, which incorporates the free ion activity model. The thesis of this article is that PM effects are likely to be more important to bioavailability than site-specific competition. Furthermore, PM effects could give the false appearance of competition even when it does not occur. The electrostatic approach can account for the bioavailability of anions, whereas the biotic ligand model cannot, and it can account for interactions among cations when competition does not occur. Finally, a simplified procedure is presented for the computation of PM for plants, and the possible use of PM in a general assessment of the bioavailability of ions is considered.
机译:质膜(PMs)带负电,这会产生负的PM表面电势(PM),该电位也由沐浴介质的离子组成控制。 PM控制离子在PM表面和介质之间的分布,从而使负电势增加阳离子的表面活性并降低阴离子的表面活性。所有阳离子均会降低PM的负性,这些常见离子按以下顺序有效:Al3 +> H +> Cu2 +> Ca2 + Mg2 +> Na + K +。这些离子,尤其是H +,Ca2 +和Mg2 +,已知会减少阳离子的吸收和生物有效性,并对阴离子产生相反的影响。毒理学家通常将有毒阳离子(通常为金属)和修饰阳离子(通常为H +,Ca2 +和Mg2 +)之间的相互作用解释为对PM表面配体结合位点的竞争。在这种包含自由离子活性模型的生物配体模型中,很少考虑使用PM。本文的论点是,PM效应对生物利用度的影响可能比针对特定地点的竞争更为重要。此外,即使没有发生PM效应,也可能导致竞争的假象。静电方法可以解释阴离子的生物利用度,而生物配体模型则不能,并且可以解释不发生竞争时阳离子之间的相互作用。最后,提出了一种简化的方法来计算植物中的PM,并考虑了PM在离子生物利用度的一般评估中的可能用途。

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