Chelator Ethylenediaminetetraacetic Acid Research Articles

X-ray photoelectron spectra of dinitrogen chelating ligands with some transition metals

The complexes of two chelating agents, CDTA ( trans-1,2-cyclohexanediaminetetraacetic acid) and EDTA (ethylenediaminetetraacetic acid), with Ni(II), Co(II) and Cu(II) are studied by means of X-ray photoelectron spectroscopy (XPS). The N1 s spectrum of CDTA has two components at 398.5 (±0.2 eV) and 400.9 (±0.2 eV) while only one signal is found after coordination at 400.0±0.2 eV. EDTA shows a N1 s spectrum with one component at 400.9±0.2eV. A negative shift of about -1.3eV is observed in its complexes. The results are compared with the literature data on the complexes in the solid state.

Calcium Regulation of Glycine Uptake by Mimosa pudica Pulvinar Cells

Summary Glycine uptake by pulvinar tissues of Mimosa pudica was inhibited by citrate and this effect was reversed by addition of CaCl2 in the incubation medium. The promotive effect of calcium may occur in a definite concentration range since glycine uptake was hindered by addition of CaCl2 at concentrations higher than 10-4M in a Mes buffered medium. Functional implication of calcium was also indicated by the inhibition noted when motor tissues were Ca2+-depleted by incubation with the calcium chelators ethylenediaminetetraacetic acid (EDTA) and more specifically ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), or were treated by the calcium antagonist LaCl3. By contrast, a stimulation of glycine transport was obtained after treatment with the calcium ionophore A23187. No close relationship was found between the action induced by these calcium modulators on the glycine uptake and the long-termed effects triggered on the transmembrane potential. From this, it can be argued for a particular calcium effect on the H+-glycine cotransport mechanism without affecting merely the proton motive force.

Modification of Integrin-Mediated Cell Attachment to Substrata by Serine Proteinases in the Presence and Absence of Divalent Cations

The sensitivity to serine proteinases of cellular proteins involved in cell-matrix adhesion was investigated using C32 melanoma cells. Cells dissociated from monolayers by the metal chelator ethylenediaminetetraacetic acid were incubated with proteolytic enzymes, and then attachment was quantified by standard cell adhesion assays. The effect of proteinases was found to depend on the presence of Ca2+ in the incubations. Incubation with 100 nM trypsin or chymotrypsin for 1-2 h (37°C) in the absence of Ca2+ reduced cell attachment to vitronectin (Vn), fibrinogen (Fb), laminin, and fibronectin by approximately 80, 80, 40, and 30%, respectively. Viability studies indicated that such treatment with proteinases was not cytotoxic. Inclusion of 0.1 mM CaCl2 in the incubations prevented the loss in attachment to all substrata. In the case of Fb, proteinase treatment in the presence of Ca2+ had an additional effect; it improved cell attachment to this substratum by about 50%. C32 cells have been shown to express the integrin αvβ3 (Vn receptor) which mediates attachment to Vn and Fb in a GRGDS-sensitive manner. Attachment of C32 cells to Vn and Fb prior to proteinase treatment and after proteinase treatment in the presence of Ca2+ was 90% inhibited by the addition of GRGDS peptide to the attachment assays. These results suggest that the adhesion observed both before and after proteinase treatment was mediated by this integrin. Analysis of the Vn receptor from proteinase-treated cells by immunoblotting of cell extracts and by SDS gel electrophoresis of immunoprecipitated receptor revealed no detectable change in either the αv or β3 subunit that correlated with loss in attachment. Similarly proteinase treatment in the presence of Ca2+ did not produce detectable alterations in the subunits which might correlate with the improved attachment to Fb. Consistent with these results, an enzyme-linked immunoassay to quantify cell surface receptors revealed little difference in the amount of Vn receptor on cells treated with proteinase in the presence or absence of Ca2+. Degradation of the αv subunit was demonstrated, however, at proteinase concentrations higher than those required to effect cell attachment. Thus, treatment of cells with serine proteinases can effect integrin-mediated attachment to matrix proteins in a manner moderated by Ca2+, but the alterations in attachment do not appear to be accompanied by detectable proteolytic modification of the integrin.

Effects of iron and chelation on Lake Kinneret bacteria

The response of natural populations of bacteria (prepared by passing Lake Kinneret water through 1 μm filters) to additions of Fe(2+) and/or the chelator ethylenediaminetetraacetic acid (EDTA) was followed by measuring the incorporation of (3)H-thymidine into >0.2 μm particulates, and also by determining the increments in cell numbers after 24 h. In most cases, a stimulation of (3)H-thymidine incorporation was observed in supplemented samples relative to untreated controls after 3 and 24 h incubation. The increase in bacterial numbers was also enhanced by these supplements. Generally, EDTA alone evoked a greater stimulation than Fe(2+); combined supplements gave no further increase. This response pattern appeared consistently throughout the year in samples taken from near-surface lake waters. These results suggest that the availability of iron or chelators may play an important role in regulating bacterial metabolism and growth even in aquatic ecosystems like Lake Kinneret where ambient concentrations of total Fe are relatively high.

Effects of the Ca 2+ chelators EGTA and EDTA on ethanol- or stress-induced gastric mucosal lesions and gastric secretion

Ca 2+ modulates gastric function and dysfunction as well as the release of cysteine proteases and metalloproteinases which have been implicated in the pathogenesis of gastric mucosal lesions. We thus tested the hypothesis that pretreatment with the Ca 2+ chelators, ethylene diamine tetraacetic acid (EDTA) and ethylene glycol-bis(β-aminoethyl ether)-N,N,N′, N′ -tetraacetic acid (EGTA) might reduce the experimental gastric mucosal damage induced by restraint cold stress or 1.0 ml of 75% ethanol. Other rats were prepared with chronic indwelling gastric cannulas and the effects of EDTA and EGTA on conscious basal gastric acid output were assessed. In addition, rats were pretreated with EGTA and EDTA prior to pylorus ligation and their effects on acid and pepsin output assessed. Both EDTA and EGTA reduced significantly the extent of ethanol-induced gastric mucosal damage as well as the degree of stress-induced gastric lesions. To further characterize the mechanism of Ca 2+ chelator protection against ethanol-induced gastric lesions, some rats were vagotomized or adrenalectomized prior to treatment with EGTA or EDTA, followed by ethanol or stress. Both adrenalectomy and vagotomy abolished gastroprotection by EGTA and slightly reduced that induced by EDTA in both models of experimental gastric mucosal injury. Both EDTA and EGTA reduced significantly basal gastric acid output, an effect which persisted for at least 2 h following their administration. Both compounds also decreased significantly acid and pepsin output in pylorus-ligated rats. We conclude that Ca 2+ chelators attenuate both acid-dependent and acid-independent gastric lesions. The effects of EGTA and EDTA likely involve, at least in part, vagal and glucocorticoid/catecholamine mediation, since vagotomy and adrenalectomy completely blocked and reduced, respectively, their protective influence on the gut.

Fenton reagents may not initiate lipid peroxidation in an emulsified linoleic acid model system

This study includes two parts. First, the Fe 2+ autooxidation and chelation processes in the presence of the chelators ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA) were studied by measuring UV light absorbance alterations. Competition for Fe 3+ between chelators and water or phosphate buffer (PB) ions was confirmed. The addition of EDTA or DTPA to Fe 3+ in water or PB only slowly turned the water/PB-Fe 3+ complexes to EDTA-Fe 3+ or DTPA-Fe 3+ complexes. In the second part of this study, the initiation mechanisms of Tween 20 emulsified linoleic acid peroxidation under stimulation by chelator-Fe-O 2 complexes were studied by measuring changes in UV light absorbance following diene conjugation. Fe 3+ in the presence of EDTA or DTPA did not stimulate diene conjugation. Fe 2+ (0.10 mM) and EDTA (0.11 mM) stimulated diene conjugation of the linoleic acid emulsion, but only after apparent Fe 2+ autooxidation. Fe 2+ and DTPA, as well as premixed DTPA-Fe 2+ complex, resulted in very fast diene conjugation in a wide range of concentrations. A nonlinear, mainly square root relation between Fe 2+ concentration and peroxidation rate was noted. Superoxide dismutase (SOD), catalase, and mannitol did not prevent the lipid peroxidation. H 2O 2 substantially decreased the DTPA-Fe 2+ stimulated, otherwise rapid, diene conjugation but slightly enhanced the slower one stimulated by EDTA-Fe 2+. Without ambient oxygen, Fenton reagents did not result in ·H abstraction-related diene conjugation. The findings suggest that ·OH resulting from Fenton reagents may not be the main cause for the initiation of peroxidation in this model system. Furthermore, a study with different combinations of Fe 2+ and Fe 3+ did not support the Fe 2+/Fe 3+ (1:1) optimum ratio hypothesis. We therefore conclude that perferryl ions or chelator-Fe-O 2 complexes may be responsible for the first-chain initiation of lipid peroxidation, at least in this model system.

Spatial and temporal visualization of a pH-dependent complexation equilibrium by nuclear magnetic resonance imaging

Alteration of a chemical equilibrium, ethylenediaminetetraacetic acid chelation of aqueous copper, in response to a pH gradient that protonates the complexing agent, has been observed spatially and temporally by 1H nuclear magnetic resonance. Protonation of the complexing agent shifted the complexation equilibrium towards free copper ion. Free and bound copper ions alter the spin lattice relaxation time (T1) of water in the host polyacrylamide gel to different extents. Based on this difference, a T1 weighted (fast repetition time, short echo time) two-dimensional spin-warp imaging sequence mapped out the distribution of the free and bound species. Addition of a pH 3 aqueous solution to the gel was insufficient to alter the equilibrium; a pH 1 aqueous solution liberated the complexed copper. Quantitative one-dimensional experiments gave a T1 weighted profile that showed the reaction front is displaced a distance proportional to the square root of time.

Investigations of iron coordination and redox reactions in seawater using 59Fe radiometry and ion-pair solvent extraction of amphiphilic iron complexes

Iron coordination and redox reactions in synthetic and coastal seawater were investigated at nanomolar concentrations using 59Fe radiometry and ion-pair solvent extraction of iron chelated by sulfoxine (8-hydroxyquinoline-5-sulfonate) and BPDS (bathophenanthroline disulfonate). Using sulfoxine, we determined the rate at which the monomeric Fe(III) hydroxide species present in seawater of pH 8 are complexed by the microbial siderophore deferriferrioxamine B and the synthetic chelator EDTA (ethylenediaminetetraacetic acid). Forward rate constants of 2 × 10 6M −1s −1 and 20 M −1s −1, respectively, were obtained. The kinetics of these reactions have not been measured previously at pH values near that of seawater. Conditional equilibrium constants measured for the Fe(III)-EDTA system are consistent with published stability constants for EDTA complexes and for Fe(III) hydrolytic equilibria minus the neutral Fe(OH) 3 o species, suggesting it is not quantitatively significant near pH 8. Commercial humic acid was found to have sufficient affinity for iron to compete with Fe(III) hydrolysis in seawater, and limited evidence was obtained for an interaction with dissolved organic matter in coastal seawater. In our investigations of redox reactions using BPDS to trap Fe(II) produced in the medium, we observed enhanced photoreduction of Fe(III) by humic acid as well as reduction induced by solutes released from phytoplankton in seawater of pH 8. Although the method is sensitive enough to work at near-oceanic levels of iron, the difficulty in distinguishing Fe(II) generated by Fe(III)-BPDS interactions from Fe(II) produced by other means limits its utility. This analytical ambiguity may be generalizable to other methods which measure ferrous iron in seawater using Fe(II)-specific ligands.

A RAPID, DIRECT CHEMICAL ASSAY FOR THE QUANTITATIVE DETERMINATION OF THIOBARBITURIC ACID REACTIVE SUBSTANCES IN RAW, COOKED, AND COOKED/STORED MUSCLE FOODS

ABSTRACTA study was performed to compare two procedures for the determination of thiobarbituric acid (TBA) levels in meat, i.e., the widely accepted distillation procedure versus a more rapid and direct extraction technique. Both methods produced statistically identical values for the rate of increase in TBA levels upon storage of precooked muscle foods. Addition of the antioxidant propyl gallate (PG) and the chelator ethylenediaminetetraacetic acid (EDTA) at concentrations of 200 ppm and 400 ppm, respectively, to the tissue samples prior to homogenization was found to be necessary both to retard further lipid oxidation and to serve as a ‘blank’or control to distinguish the color products formed between malondialdehyde (MDA) and TBA with those produced between other peroxides and TBA. The need for use of a control appears to be species dependent.

Effects of three chelating agents, EDTA, NTA, and TPP, on the concentration of elements in rat tissues

Ethylene diamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and tripolyphosphate (TPP) sodium salts were given orally to rats at the dose of 1 mmol/kg/d for 35 d. The concentrations of Na, K, Ca, Mg, P, S, Fe, Sr, Cu, and Zn were determined in blood, plasma, brain, heart, muscle, liver, kidney, duodenum, and bone of control rats and of the rats receiving EDTA, NTA, and TPP. The main effect induced by EDTA, NTA, and TPP was a decrease of the concentrations of several elements Ca, Mg, Fe, P in the duodenum. Otherwise, EDTA induced an increase of Zn in the kidney (+ 20%), NTA, an increase of Fe in liver (+ 29%), and particularly an increase of Zn in bone (+ 44%). TPP induced a slight decrease of Zn and Cu in liver. In conclusion, EDTA, NTA, and TPP taken orally at the dose of 1 mmol/kg/d for 35 d induced moderate changes of the concentrations of some elements in rat tissues, but without signs of toxicity.

Effect of repeated occupational exposure to lead, cessation of exposure, and chelation on levels of lead in bone

A sensitive K-X-ray fluorescence (K-XRF) instrument was used to measure lead levels in the tibia and patella on a series of twelve subjects who had relatively well-documented histories of lead exposure and blood lead levels. For some subjects, K-XRF measurements were taken at multiple points in time, and before and after chelation with EDTA (ethylenediamine tetraacetic acid). Results confirm that K-XRF measured bone lead levels correspond to cumulative blood lead indices and not to current blood lead levels. Moreover, the data suggest that bone lead levels; (1) correspond to urinary lead following the EDTA mobilization test unless previous chelation has occurred; (2) rise initially after lead exposure ceases and blood lead levels decrease, probably from redistribution from soft tissue, and then fall; and (3) do not decrease with a 3- to 5-day course of therapeutic EDTA chelation. K-XRF levels in the patella were noted to decrease more rapidly than levels in the tibia after cessation of lead exposure, a finding that probably reflects the greater turnover of lead in trabecular bone than in cortical bone.

Hydrogen peroxide formation and iron ion oxidoreduction linked to NADH oxidation in radish plasmalemma vesicles

Previously, we showed the presence in radish ( Raphanus sativus L.) plasmalemma vesicles of an NAD(P)H oxidase, active at pH 4.5–5.0, which elicits the formation of anion superoxide (Vianello and Macri (1989) Biochim. Biophys. Acta 980, 202–208). In this work, we studied the role of hydrogen peroxide and iron ions upon this oxidase activity NADH oxidation was stimulated by ferrous ions and, to a lesser extent, by ferric ions. Salicylate and benzoate, two known hydroxyl radical scavengers, inhibited both basal and iron-stimulated NADH oxidase activity. The iron chelators EDTA (ethylenediaminetetraacetic acid) and DFA (deferoxamine melysate) at high concentrations (2 mM) inhibited the NADH oxidation, whereas they were ineffective at lower concentrations (80 μM); the subsequent addition of ferrous ions caused a rapid and limited increase of oxygen consumption which later ceased. Hydrogen peroxide was not detected during NADH oxidation but, in the presence of salicylate, its formation was found in significant amounts. NADH oxidase activity was also associated to a Fe 2+ oxidation which was only partialy inhibited by salicylate. Ferrous ion oxidation was partially inhibited by catalase and prevented by superoxide dismutase, while ferric ion reduction was abolished by catalase and unaffected by superoxide dismutase. These results show that during NADH oxidation iron ions undergo oxidoreduction and that hydrogen peroxide dismutase. These results show that during NADH oxidation iron this oxidation appears linked to the univalent oxidoreduction of iron ions by a reduced flavoprotein of radish plasmalemma which is then converted to a radical form. The latter, reacting with oxygen generates the superoxide anion which dismutates to H 2O 2. Hydrogen peroxide, through a Fenton's reaction, may react with Fe 2+ to produce hydroxyl radicals, or with Fe 3+ to generate the superoxide anion.

Reaction of ferric iron by siderophore produced by abradyrhizobiumstrain

Abstract Ferric iron (Fe+3) chelating compounds, including siderophores produced by microorganisms, help in the Fe nutrition of plants. Dicotyledonous plants absorb Fe in the ferrous (Fe+2) form. The ability of siderophores produced by a Brady ‐rhizobium strain, a rhizosphere bacterium of groundnut (Arachis hypogaea), to reduce Fe+3 was tested. Two Fe+3 (58Fe) binding fractions were separated from the culture supernatant of a Bradyrhizobium strain grown in an iron deficient medium. One of the fractions isolated reduced Fe+3 to Fe+2, unlike the synthetic chelator ethylenediaminetetraacetic acid (EDTA). It has been proposed that Fe‐chelators supply Fe+3 to groundnut roots, and Fe+3 reduction to Fe+2 and its uptake occurs at the plasmalemma. Since siderophores can reduce Fe+++, they may help in Fe nutrition of groundnut plants better than chelators like EDTA. There is no evidence to indicated siderophore uptake by groundnut plants, but we have detected ethyl acetate insoluble Fe+3 reducing activity in the xy...

Effect of EDTA on the photocatalytic activities and flatband potentials of cadmium sulfide and cadmium selenide

Photocatalyzed hydrogen evolution on Pt-loaded CdS powder from aqueous solutions of sodium sulfite is enhanced by addition of a small amount of ethylenediaminetetraacetic acid (EDTA) to the solution. EDTA is hardly consumed by the reaction. It has been concluded from the measurements of the flat-band potential of CdS electrodes that EDTA and other chelating agents, such as 1,2-cyclohexanediaminetetraacetic acid and nitrilotriacetic acid, are adsorbed strongly on the surface of CdS and shift the conduction band energy toward the negative. The enhancement of the photocatalytic hydrogen evolution by the addition of EDTA is explained as being caused by the upward shift of the conduction band energy of CdS due to the negative charge of the chelating agents. The change of the conduction band energy by the adsorption of EDTA is observed also for CdSe electrodes. Although Pt-loaded CdSe powder is inactive for the hydrogen evolution from aqueous solutions of sodium sulfite, it generates hydrogen when EDTA is added to the solution.

Studies on prolonged acute regional ischemia: I. Evidence for preserved cellular viability after 6 hours of coronary occlusion

Six hours of coronary occlusion has been thought to produce extensive and irreversible transmural damage and no possibility of salvage by reperfusion. This has been based on findings of adenosine triphosphate depletion and histochemical (triphenyltetrazolium chloride nonstaining) and ultrastructural changes (conventional preparatory techniques). This study tests the hypothesis that, in contrast to conventional wisdom, considerable structural and mitochondrial functional integrity remains in cardiac muscle subjected to 6 hours of regional ischemia. Twenty open-chest anesthetized dogs underwent isolation of the left anterior descending coronary artery and were observed for 6 hours. Eight of the 20 did not undergo ischemia and served as controls. Twelve underwent 6 hours of proximal ligation of the left anterior descending coronary artery (30% +/- 2% area at risk). Transmural biopsy specimens were analyzed. Coronary occlusion reduced regional blood flow (radioactive microspheres) to less than 10 ml/100 gm/min (p less than 0.05) and dyskinesia persisted in the area at risk for 6 hours. High-energy phosphates (adenosine triphosphate and creatine phosphate) declined to negligible levels and histochemical damage occurred (49% +/- 12% triphenyltetrazolium chloride non-staining). Mitochondrial ultrastructural changes (low protein denaturation embedding technique) were mild (the integrity of the inner and outer mitochondrial surface membranes and crystal membranes was maintained and myofibrillar degeneration did not occur). Mitochondrial oxidative phosphorylation rate remained at 63% of control levels, respiratory control index remained at 77%, and adenosine diphosphate/oxygen ratio was maintained at 96%. Mitochondrial Ca++ increased with lanthanum (from 26 to 46 nmol/mg protein, p less than 0.05), but irreversible calcium precipitation did not occur; calcium could be mobilized to normal levels (i.e., 13 nmol/mg protein) by ethylenediaminetetraacetic acid chelation. These data support our inference that necrosis does not occur after 6 hours of coronary occlusion and suggest that muscle salvage by reperfusion is possible after at least 6 hours of regional myocardial ischemia.

The cell-bound proteinase system of Lactobacillus casei — purification and characterization

The cell-wall crude extract from Lactobacillus casei NCDO 151 was partially purified by DEAE-Sephacel chromatography. Three active fractions were eluted. Two major peaks (eluted with 0.05 M and 0.27 M phosphate buffer) were further investigated. Peak I represented enzymatic activity with an optimum temperature of 40°C, an optimum pH of 7.0 and was strongly inhibited by the serine proteinase inhibitor phenylmethylsulfonylfluoride. Peak II represented an enzymatic activity with an optimum temperature of 45°C, an optimum pH of 7.5 and was totally inhibited by p-hydroxymercuribenzoate. None of the enzymes was affected by the metal chelator ethylenediaminetetraacetic acid at a concentration up to 1 × 10 −2.

REGENERATION OF BLUE AND PURPLE MEMBRANES FROM DEIONIZED BLEACHED MEMBRANES OF Halobacterium halobium

Abstract— Bleached purple membrane normally binds Ca2+ and Mg2+, which can be removed by the divalent cation chelator ethylenediaminetetraacetic acid (EDTA). Regeneration of pigments from EDTA‐treated bleached membrane (apomembrane) and retinal leads to the formation of blue membrane at pH 4.8, and purple membrane at neutral pH. The pigments take much longer to regenerate than with un‐deionized apoprotein. Adding back cations to the deionized apomembrane only partially speeds up the regeneration process. Like native purple membrane, the regenerated purple membrane also undergoes a photocycle and shows a light‐induced proton release and uptake, although with much slower kinetics than the native species. Thus, cations control the kinetics of pigment regeneration, and also some aspects of the pigment's conformation which controls the photocycle kinetics. The removal and replacement of the cations is not completely reversible, suggesting the cations are not merely bound in the double layer.

Effect of Phosphorus and Zinc Fertilization on the Solubility of Zn2+ in Two Alkaline Soils

AbstractConcentrations of Zn2+ in equilibrium with two alkaline soils were calculated from the reactions of EDTA (ethylenediaminetetraacetic acid) chelates. The initial speciation of EDTA was varied to allow equilibrium with Zn2+ concentrations in the soil to be approached from above and below. Fertilizer Zn was added at 0 to 5 mg kg−1 as ZnSO4 and reacted thoroughly with the soil before additions of P or EDTA chelates. Phosphorus was added at 0 or 62 mg kg−1 as a mixture of KH2PO4 and K2HPO4. Concentrations of soluble Zn2+ in unfertilized soil were extremely low, approximately 5 × 10−10 M in the noncalcareous soil at pH 7.2 and 1 × 10−10 M in the calcareous soil at pH 7.6. These Zn2+ concentrations were raised 7‐ to 14‐fold by 5 mg kg−1 of added Zn, and the higher levels persisted for at least 11 weeks. Buffering of Zn2+ by the soils was substantial, ranging from about 15 to 45 (nmol g−1)/(nmol L−1). Additions of P caused small decreases in the concentrations of Zn2+ and other divalent cations in solution. Only in the Zn‐fertilized calcareous soil were the percent decreases in Zn2+ greater than those of the major divalent cations, Ca2+ and Mg2+. This effect of P in the calcareous soil is of special interest because of its apparent selectivity for Zn, but the effect was small as shown by reductions of only 12 to 19% in the [Zn2+]/[Ca2+ + Mg2+] concentration ratio.

Investigation of soluble indium chelates for groundwater and hydrothermal fluid tracing

Indium is an excellent tracer with a unique combination of good activation analysis sensitivity retaining most of the advantages of radioactive tracers without creating health or environemental risk, and low background concentration in surface and subsurface fluids. The organic chelating agents ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) were selected to enhance the solubility of In as a tracer within the pH range of groundwater and hydrothermal fluids. The thermal stability of indium chelates of EDTA and NTA was investigated at temperatures from 22 to 240°C. Degradation of In(III)-EDTA, observed at and above 200°C, is attributed to metal dissociation followed by thermal decomposition of the organic ligand. Degradation of In(III)-NTA, observed at temperatures greater than 150°C, is probably due to significant decrease of the thermodynamic formation constant. The results suggest that soluble indium chelates can be used effectively as tracers for surface and groundwater flow and transport studies. The applicability of In(III)-EDTA as a conservative tracer can be extended to low-temperature geothermal reservoirs where ionic chemical tracers are not fully conservative.

Cytotoxicity of metals, metal-metal and metal-chelator combinations assayed in vitro

A simple, rapid assay, based on the lysosomal incorporation of neutral red by cells, conveniently carried out in 96-well microtiter plates, was used to evaluate the cytotoxic effect of cationic and anionic metal salts on BALB/c mouse 3T3 fibroblasts. Ranking of the metals according to their decreasing potency was based on spectrophotometrically determined absorbance of the neutral red, extracted from surviving viable cells. The rank order was Cd>Hg>Ag>Zn>Mn>Cu>Co>Ni>Cr(III) for the cationic metals and Cr 2O 7>CrO 4>AsO 2>AsO 4>SeO 3>SeO 4>MnO 4 for the anionic metals tested. Cationic metals incubated with cultures in medium containing 1% fetal bovine serum (FBS) were 3–4 times more toxic than in medium with 10% FBS. Cadmium served as a representative metal for the use of this assay not only for concentration, but also for time dependent exposures. Thus a 10% cytotoxic effect after 1 h of incubation with 60 μM cadmium was increased to 90% after 6 h. Examination of the effect of metal-metal interaction on cytotoxicity showed a marked reduction of cadmium toxicity by zinc and to a lesser degree, by nickel. The neutral red assay was also effectively used to investigate the effect of the chelators ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and 2,3-dimercaptosuccinic acid (DMSA) on cadmium-induced injury. Cytotoxicity by cadmium was completely inhibited by EDTA, and partially by NTA, but DMSA was ineffective. Reduction of copper toxicity by chelation was less efficient than for cadmium. Use of a chelator as therapy against metal poisoning was only partially effective and limited to administration within 2 h after incubation of cells with cadmium. It is believed that the neutral red assay can be valuable tool for the screening of cytotoxic and potentially therapeutic agents under controlled in vitro conditions.