Plasma membrane surface potential (ψpm) as a determinant of ion bioavailability: A critical analysis of new and published toxicological studies and a simplified method for the computation of plant ψpm

Kinraide, Thomas B.

doi:10.1897/06-103r.1

Cited by 82 publications

(102 citation statements)

References 38 publications

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“…Regardless, the improvements in the r 2 values demonstrate the importance of the dual effects of c 0 o upon plant growth. For a reanalysis of published soil studies demonstrating the first effect of c 0 o in soils, see Kinraide (2006).…”

Section: Modeling Ion Uptake and Toxicity With Electrostatic Models (mentioning

confidence: 99%

“…Measured RRE of wheat seedlings exposed to Al 3+ affected by Ca 2+ and Mg 2+ . Data were taken from Kinraide et al (1992;experiment 14 petition), such mechanisms appear to be unimportant in many cases (Kinraide, 2006;Wang et al, 2008). In those cases, including those in this study, the dual effects of c 0 o are sufficient to explain the ion-toxicant interactions (Kinraide, 2006;Wang et al, 2008; this study).…”

Section: General Evaluation Of the Electrostatic Approach To Ion Uptamentioning

confidence: 99%

“…However, the BLM as the main determinant of toxicant bioavailability does not deserve uncritical acceptance, and the mechanism of the ameliorative effectiveness of cations must be considered carefully, especially in light of cation enhancement of anion toxicity (Kinraide, 2006). Previous studies (Kinraide, 2006;Wang et al, 2008) showed that global electrostatic interactions at the plasma membrane (PM) exterior surfaces, rather than site-specific mechanisms, may play the dominant role in the phytotoxicity of metals.The process of metal uptake typically encompasses diffusion of the ion to the cell surface, speciation reactions, electrostatic interactions, and subsequent transport across PMs (Hille, 2001; Kinraide, 2001). The PM electrical properties play key roles in the distribution of ions at the exterior surface of PMs, in ion transport across PMs, and, hence, in ion intoxication.…”

mentioning

confidence: 99%

“…The scientific and regulatory communities have become interested in the BLM and have incorporated it into regulations. However, the BLM as the main determinant of toxicant bioavailability does not deserve uncritical acceptance, and the mechanism of the ameliorative effectiveness of cations must be considered carefully, especially in light of cation enhancement of anion toxicity (Kinraide, 2006). Previous studies (Kinraide, 2006;Wang et al, 2008) showed that global electrostatic interactions at the plasma membrane (PM) exterior surfaces, rather than site-specific mechanisms, may play the dominant role in the phytotoxicity of metals.…”

mentioning

confidence: 99%

“…The common neglect of c 0 o is inconsistent with its importance and may reflect the difficulty of measuring c 0 o . Nevertheless, several studies have considered physiological phenomena in terms of c 0 o (Barber, 1980;McLaughlin, 1989;Zhang et al, 2001;Kinraide, 2003aKinraide, , 2006Yermiyahu and Kinraide, 2005;Wang et al, 2008;Kinraide and Wang, 2010;Kopittke et al, 2010), and a fully parameterized GouyChapman-Stern (GCS) model is now available for calculating c 0 o (Wang et al, 2008;Kinraide and Wang, 2010). The aims of this study were (1) to emphasize the importance of the PM electrical properties for the transport and toxicity of ions while developing electrostatic models for uptake and toxicity, (2) to determine possible multiple effects of c 0 o upon ion uptake and toxicity, and (3) to apply electrostatic models, incorporating membrane surface-to-surface activities and electrical gradients, to predict the uptake and toxicity of metal ions for use in risk assessment in natural waters and soils.…”

mentioning

confidence: 99%

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Plasma Membrane Surface Potential: Dual Effects upon Ion Uptake and Toxicity

et al. 2010

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Electrical properties of plasma membranes (PMs), partially controlled by the ionic composition of the exposure medium, play significant roles in the distribution of ions at the exterior surface of PMs and in the transport of ions across PMs. The effects of coexisting cations (commonly Al 3+ , Ca 2+ , Mg 2+ , H + , and Na + ) on the uptake and toxicity of these and other ions (such as Cu 2+ , Zn 2+ , Ni 2+ , Cd 2+ , and H 2 AsO 4 -) to plants were studied in terms of the electrical properties of PMs. Increased concentrations of cations or decreased pH in rooting media, whether in solution culture or in soils, reduced the negativity of the electrical potential at the PM exterior surface (c 0 o ). This reduction decreased the activities of metal cations at the PM surface and increased the activities of anions such as H 2 AsO 4 -. Furthermore, the reduced c 0 o negativity increased the surface-to-surface transmembrane potential difference, thus increasing the electrical driving force for cation uptake and decreasing the driving force for anion uptake across PMs. Analysis of measured uptake and toxicity of ions using electrostatic models provides evidence that uptake and toxicity are functions of the dual effects of c 0 o (i.e. altered PM surface ion activity and surface-to-surface transmembrane potential difference gradient). This study provides novel insights into the mechanisms of plant-ion interactions and extends current theory to evaluate ion bioavailability and toxicity, indicating its potential utility in risk assessment of metal(loid)s in natural waters and soils.Some solutes in growth media, such as cations and organic matter, influence the bioavailability and toxicity of metals in natural waters and soils (Peijnenburg et al., 1997;Weng et al., 2004;Kopittke et al., 2010). Novel insights into the bioavailability and toxicity of metals have inspired the development of models in order to allow accurate impact assessments of metals emitted into the environment. The biotic ligand model (BLM; Di Toro et al., 2001), as an extension of the free ion activity model (FIAM), incorporates site-specific competitions among cations (commonly Ca 2+ , Mg 2+ , and H + ) and ionic toxicants (commonly heavy metals) for binding to a biotic ligand at the cell surface. The scientific and regulatory communities have become interested in the BLM and have incorporated it into regulations. However, the BLM as the main determinant of toxicant bioavailability does not deserve uncritical acceptance, and the mechanism of the ameliorative effectiveness of cations must be considered carefully, especially in light of cation enhancement of anion toxicity (Kinraide, 2006). Previous studies (Kinraide, 2006;Wang et al., 2008) showed that global electrostatic interactions at the plasma membrane (PM) exterior surfaces, rather than site-specific mechanisms, may play the dominant role in the phytotoxicity of metals.The process of metal uptake typically encompasses diffusion of the ion to the cell surface, speciation reactions, electrostatic interac...

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Section: Modeling Ion Uptake and Toxicity With Electrostatic Models (mentioning

confidence: 99%

Section: General Evaluation Of the Electrostatic Approach To Ion Uptamentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Plasma Membrane Surface Potential: Dual Effects upon Ion Uptake and Toxicity

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Actinide Speciation and Bioavailability in Fresh and Marine Waters

Markich¹,

Brown²

2018

Encyclopedia of Inorganic and Bioinorganic Chemistry

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The actinides comprise a group of 15 metals (with atomic numbers ranging from 89 to 103) that are all radioactive and occur as cations in natural surface waters. Only the first 10 actinides are covered in this study, as these are the most environmentally relevant, where the dominant oxidation states are as follow: actinium(III), thorium(IV), protactinium(V), uranium(VI), neptunium(V), plutonium(IV) and (V), americium(III), curium(III), berkelium(III), and californium(III). The physicochemical form, or speciation, of an actinide (e.g., free metal ion, or complexes with inorganic or organic ligands) in natural surface waters can be determined using a range of analytical techniques. However, such methods are seldom commercially available and rarely determine a complete distribution of all metal species. A complementary approach, which is more cost effective, time efficient, and predictive, is the application of geochemical speciation modeling, which calculates the percentage distribution of all actinide species based on known or postulated chemical reactions. The general consensus is that geochemical speciation models can provide useful results if applied correctly with an understanding of the differences between simulated and real systems. This is the first study to use an internally consistent equilibrium database within a geochemical model (WHAM) to calculate the speciation of the first 10 actinides across fresh, estuarine, and marine waters that incorporates natural dissolved organic matter (DOM) (i.e., fulvic acid). The speciation of a metal (actinide) largely governs its uptake and/or toxicity (bioavailability) in aquatic organisms. The general consensus is that bioavailability is best predicted by the concentration of the free metal ion (M z+ ) and that metals complexed with most inorganic ligands (e.g., carbonate or sulfate) or natural DOM, typically have low bioavailability. There is also evidence to suggest that colloidal thorium is bioavailable to freshwater organisms. The study correlates observed actinide speciation with bioavailability (where available) or utilizes predicted actinide speciation to determine the likely magnitude of bioavailability, as applied to aquatic organisms. This study also addresses the likely effects of global ocean acidification and increased natural DOM concentrations in fresh surface waters on actinide speciation and bioavailability.

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Evaluating the biotic ligand model for toxicity and the alleviation of toxicity in terms of cell membrane surface potential

Wang

Zhou

et al. 2010

Environmental Toxicology and Chemistry

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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 Ca2+, Mg2+, H+, Na+, K+, etc.) in bulk-phase medium reduce the negativity of CM surface electrical potential (psi0), but these slightly increase the driving force of a metal ion crossing CMs (surface-to-surface transmembrane potential difference, Em,surf). Toxicologists commonly attributes the interactions between heavy metals and common cations (e.g., H+, Ca2+, and Mg2+) to competitions for binding sites at a hypothetical CM surface ligand. The psi0 effects are likely to be more important to metal toxicity and the alleviation of toxicity than site-specific competition. Models that do not consider psi0, 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 psi0 effects and site-specific competition effects was developed to evaluate metal (Cu2+, Co2+, and Ni2+) 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.

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Plasma membrane surface potential (ψpm) as a determinant of ion bioavailability: A critical analysis of new and published toxicological studies and a simplified method for the computation of plant ψpm

Cited by 82 publications

References 38 publications

Plasma Membrane Surface Potential: Dual Effects upon Ion Uptake and Toxicity

Plasma Membrane Surface Potential: Dual Effects upon Ion Uptake and Toxicity

Actinide Speciation and Bioavailability in Fresh and Marine Waters

Evaluating the biotic ligand model for toxicity and the alleviation of toxicity in terms of cell membrane surface potential

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