Concentrations Of Pb2 Research Articles

Characteristics of Soil Lead Tolerance, Accumulation and Distribution in Salix babylonica Linn. and Salix jiangsuensis J172

Patience plants provide a good way for phytoremediation of environmental pollution. In this paper,two willow species,Salix babylonica Linn. and S. jiangsuensis J172 were selected to test the lead tolerance,lead accumulation and distribution in plants through pot experiments with different soil Pb concentrations. The results showed that a significantly negative correlation relationship existed between S. babylonica and soil available lead,the biomass of root for Salix insignificantly decreased under low concentrations of Pb2 +at a variation of0- 1 200 mg· kg- 1and 0- 800 mg · kg- 1for S. babylonica Linn. and S. jiangsuensis J172,respectively,which suggested that S. babylonica Linn. had a better tolerance than S. jiangsuensis J172 under Pb2 +stress. The root length,root surface area,root volume and root diameter of both willow species decreased with the increase of soil Pb2 +concentration. At Pb2 +concentration of 1 600 mg·kg- 1,the root length,root surface area,root volume and root diameter of S. babylonica Linn. and S. jiangsuensis J172 decreased by 50. 40%,45. 15%,44. 44%,9. 10%,and 45. 00%,45. 88%,47. 02%,37. 14%,respectively,as compared with the control.Both willow species accumulated more lead in roots than that in stems and leaves,the order of lead accumulation in different organs of two kinds of willows are root stem leaf. At Pb2 +concentration of 800 mg·kg- 1,the tolerance indices of S. babylonica Linn. and S. jiangsuensis J172 were 91. 15% and 84. 26%,the uptake of lead from the soil in them reached 140. 20 and 149. 49 mg,respectively. These results indicated that these two willow species has greater potential for restoration of medium soil lead contamination.

The Effects of Pb<sup>2+</sup> Stress on the Growth and Physiological Characteristics of <i>Chlorella pyrenoidosa</i>

In the Pb2+ stress experiments, the concentrations of Pb2+ were 1, 5, 10, 50, and 80 mg/L respectively, BG11 culture medium was served as the control. The results showed that Pb2+ affected markedly on the growth and physiological characteristics of chlorella pyrenoidosa under certain concentration. As the exposure time, chlorella pyrenoidosa biomass is restrained gradually. Pb2+ also have significant inhibition to effect chlorophyll content and have an effect relationship with the malondialdehyde content of chlorella pyrenoidosa . Lead concentrations and the soluble protein content are time effect relationship . And the longer the inhibitory effect becomes more obvious. Superoxide dismutase (sod) activity increased first then decreased with the increase of the concentration of Pb2+.

Photoluminescence Properties of Combustion Synthesized BaB2O4:Pb2+ Phosphor

Inorganic borate host phosphor BaB2O4 doped with varying concentrations of Pb2+ has been prepared by a solution combustion synthesis technique. The synthesis is based on the exothermic reaction between the fuel (urea) and oxidizer (ammonium nitrate). The photoluminescence properties of prepared materials were studied at room temperature. Under the excitation of 240 nm, the phosphor BaB2O4:Pb2+ shows broad emission at 370 nm (corresponds to 3P1 to 1S0 transition). The optimum concentration of Pb2+ in BaB2O4:Pb2+ was found to be 0.02 mol (relative to Ba). The critical transfer distances, R0 were calculated. Stokes shifts were calculated (using corresponding excitation and emission band peaks) to be 14,640 cm−1. The emission bands of synthesized phosphors are in the ultraviolet (UV) region and could be potential candidates for application in UV lamps.

A portable DNAzyme-based optical biosensor for highly sensitive and selective detection of lead (II) in water sample

A portable, rapid and cost-effective DNAzyme based sensor for lead ions detection in water samples has been developed using an optical fiber sensor platform. The presence of Pb2+ cleaves the DNAzymes and releases the fluorescent labeled fragments, which further hybridize with the complementary strands immobilized on the optic fiber sensor surface. Subsequent fluorescent signals of the hybridized fluorescent labeled fragment provides quantitative information on the concentrations of Pb2+ with a dynamic range from 2–75nM with a detection limit of 1.03nM (0.21ngmL−1). The proposed sensor also shows good selectivity against other mono and divalent metal ions and thus holds great potential for the construction of general DNAzyme-based sensing platform for the monitoring of other heavy metal ions. The sensor can be regenerated with a 1% SDS solution (pH 1.9) over 100 times without significant deterioration of the sensor performance. This portable sensor system can be potentially applied for on-site real-time inexpensive and easy-to-use monitoring of Pb2+ in environmental samples such as wastewater effluents or water bodies.

Biomass fly ashes as low-cost chemical agents for Pb removal from synthetic and industrial wastewaters

The main aim of this work was to study the removal efficiency of Pb from synthetic and industrial wastewaters by using biomass fly ashes. The biomass fly ashes were produced in a biomass boiler of a pulp and paper industry. Three concentrations of Pb2+ were tested in the synthetic wastewater (1, 10 and 1000mg Pb/L). Moreover, two different wastewaters were collected in an industrial wastewater treatment plant (IWWTP) of an industry of lead-acid batteries: (i) wastewater of the equalization tank, and (ii) IWWTP effluent. All the wastewaters were submitted to coagulation–flocculation tests with a wide range of biomass fly ashes dosage (expressed as Solid/Liquid – S/L – ratios). All supernatants were characterized for chemical and ecotoxicological parameters. The use of biomass fly ashes has reduced significantly the Pb concentration in the synthetic wastewater and in the wastewaters collected in the IWWTP. For example, the definitive coagulation–flocculation assays performed over the IWWTP effluent presented a very low concentration of Pb (0.35mg/L) for the S/L ratio of 1.23g/L. Globally, the ecotoxicological characterization of the supernatants resulting from the coagulation–flocculation assays of all wastewaters has indicated an overall reduction on the ecotoxicity of the crude wastewaters, due to the removal of Pb.

重金属铅与两种淡水藻的相互作用

PDF HTML阅读 XML下载 导出引用 引用提醒 重金属铅与两种淡水藻的相互作用 DOI: 10.5846/stxb201211051545 作者: 作者单位: 安徽师范大学生命科学院,安徽师范大学生命科学院,安徽师范大学生命科学院,安徽师范大学生命科学院,安徽师范大学生命科学院,安徽师范大学生命科学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31170443） Interactions between heavy metal lead and two freshwater algae Author: Affiliation: The Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province,College of Life Sciences,Anhui Normal University,College of Life Sciences,Anhui Normal University,The Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province,College of Life Sciences,Anhui Normal University,The Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province,College of Life Sciences,Anhui Normal University,The Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province,College of Life Sciences,Anhui Normal University,The Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province,College of Life Sciences,Anhui Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了研究重金属铅与淡水藻类之间的相互作用，采用不同Pb2+浓度处理铜绿微囊藻（Microcysis aeruginosa Kutz.）和斜生栅藻,分别对两种藻的生物量、藻液电导率、O2-·含量、过氧化物酶（POD）、过氧化氢酶（CAT）活性以及藻对Pb2+的吸收作用等进行了测定，并通过扫描电镜观察了不同Pb2+浓度处理下两种藻细胞的表面结构。结果显示：（1）Pb2+浓度低于3 mg/L促进铜绿微囊藻生长，高于9 mg/L抑制其生长；但在3-12 mg/L范围内，Pb2+均明显抑制了斜生栅藻的生长，说明斜生栅藻对Pb2+毒性的敏感程度要高于铜绿微囊藻。（2）受到铅离子的胁迫，两种藻细胞膜通透性均有一定改变，扫描电子显微镜的照片观察，两种藻细胞表面的絮状物随着Pb2+的升高而增多，尤其是斜生栅藻细胞结构改变明显，多数细胞变形破裂；同时，O2-·含量升高，POD、CAT活性早期均可随Pb2+的增加而上升，表明氧自由基的产生增多以及由其引起的细胞生理生化改变可能是铅离子作用于藻细胞的主要机制。（3）两种淡水藻对Pb2+均有吸收作用，单位量藻细胞内，斜生栅藻对Pb2+的吸收能力好于铜绿微囊藻。所有结果提示：斜生栅藻不仅可以作为对重金属敏感的指示生物来监测水体Pb2+污染程度；同时由于斜生栅藻比铜绿微囊藻具有更好的Pb2+吸收能力，因此还可以利用斜生栅藻作为处理水体Pb2+的生物材料。 Abstract:To get a better understanding of interactions between heavy metal lead and freshwater algae Microcysis aeruginosa Kutz. and Scenedesmus obliquus (Turp.) Kutz., the algal biomass, electrical conductivity (EC) of supernatant, concentration of superoxide anion radical (O2-·), activities of POD and CAT as well as the absorption of Pb2+ by algal were determined respectively at different concentrations of Pb2+, and the surface structure of two algae cells was contrasted by scanning electron microscopy. The results showed as follows: (1) 3 mg/L of Pb2+ accelerated the growth of M. aeruginosa, and the opposite effects were observed when exposed to more than 9 mg/L of Pb2+; however, the growth of S. obliquus was obviously inhibited when the concentrations of Pb2+ ranged from 3 to 12 mg/L. The effects of Pb2+ on the two kinds of freshwater algae indicated that S. obliquus was more sensitive to the Pb2+ pressure. (2) The membrane permeability of the two algae cells was changed under the stress of Pb2+. The photos of scanning electron microscopy showed that the superficial flocs of the two algae cells increased with the increasing of Pb2+, and numerous cells deformed or ruptured evidently, especially for S. obliquus. Meanwhile, the increases of O-2 contents were exhibited and the activities of POD and CAT in the two algae were advanced with increasing of Pb2+ concentration at the early stage, which indicated that the main mechanisms of Pb2+ acting on two algae involve the increasing production of superoxide anion radical and the accompanying physiological and biochemical changes of the algae. (3) Pb2+ can be absorbed by the two algae, and moreover S. obliquus had higher capacity of Pb2+ absorption than M. aeruginosa did at the unit cells. From the above points, compared with the M. aeruginosa, S. obliquus can be used not only as a biological indicator for monitoring heavy metal pollution levels, but also as a biological material to deal with water Pb2+ contamination due to its ability of Pb2+ absorption. 参考文献 相似文献 引证文献

Investigation on Electrochemically Cathodic Polarization of Boron-Doped Diamond Electrodes and Its Influence on Lead Ions Analysis

The purpose of this paper is to further understand the dependence of the electrochemical activity of a boron-doped diamond (BDD) film electrode on its surface boron doping concentration and the pretreatment applied to its surface. An electrochemically cathodic polarization (−3 V vs. SCE) with a varying polarization duration (5–50 min) was carried separately out to three types of BDDs with a boron doping level of 700, 2500, 8000 ppm in 0.5 M H2SO4 solution. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to evaluate surface activity of the BDDs with and without cathodic polarizations by using 1.0 mM Fe(CN)63−/4−. Moreover, the surface activity of the polarized BDD electrodes was examined further by using anodic stripping voltammetry to detect a series of known concentrations of Pb2+. Our results indicated that the applied cathodic polarization significantly improved the surface activity of the as-received BDD, and exhibited more active effect on the surface of a higher boron doping level BDD compared to a lower boron doping level BDD, thereby improving the ability of the polarized BDDs to detect trace Pb(II) in aqueous solutions by anodic stripping voltammetry.

Simultaneous determination of trace levels of lead(II) and copper(II) by square wave stripping voltammetry using a glassy carbon electrode modified with hierarchical gold dendrites

A glassy carbon electrode was modified with gold hierarchical dendrites (Au HDs) by one-step electrodeposition in the presence of cytosine, which plays an important role in the formation of the Au HDs. This approach is simple, fast, feasible, controllable, without any seed, template, or surfactant. The modified electrodes were used for the simultaneous determination of Pb2+ and Cu2+ by square wave stripping voltammetry. The peak currents show good linear relationship with concentrations of Pb2+ and Cu2+ in the range of 5.0 to 15.0 μM. The recoveries of the spiked water samples are in the range of 94.0 %–107.4 % for Pb2+ and Cu2+, and their relative standard deviation are in the range of 2.7 %–4.3 % for Pb2+ and Cu2+, respectively (n = 3).

Enhanced lead adsorption by unbleached newspaper pulp modified with citric acid

A thermochemical method was performed to enhance lead adsorption of unbleached newspaper pulp. Unbleached pulp was obtained after mechanical treatment of waste newspaper and was chemically modified with citric acid (CA) at 90°C for 90min. The parameters under investigation were the pH of adsorption solution (3–9), the concentration of mechanically and chemically treated pulps (0.1–1g), the concentration of CA (0.5M and 1M), the initial concentration of lead (20–1000mg/l) and the pulp-lead solution contact time (0–24h). The maximum adsorption capacity of mechanically treated newspaper pulp (MT-pulp) increased by 35% (25.71mg/g) after modification with 0.5M CA and 82% (34.6mg/g) with 1M CA. The modification process resulted in higher negative values of zeta potential and surface charge of mechanically treated pulp reaching the highest charge and maximum lead adsorption at pH=6. The adsorption experimental data fitted well to the Langmuir isotherm model and inferred that adsorption and ion-exchange are major mechanisms for binding Pb2+ ions. Kinetic studies for three different concentrations of Pb2+ showed that the adsorption process involved two stages and the experimental data followed the pseudo-second order model. The results showed that CA-modified newspaper pulp is an effective adsorbent for the removal of Pb2+ from wastewater.

DNAzyme-based highly sensitive electronic detection of lead via quantum dot-assembled amplification labels

An electronic DNAzyme sensor for highly sensitive detection of Pb2+ is demonstrated by coupling the significant signal enhancement of the layer-by-layer (LBL) assembled quantum dots (QDs) with Pb2+ specific DNAzymes. The presence of Pb2+ cleaves the DNAzymes and releases the biotin-modified fragments, which further hybridize with the complementary strands immobilized on the gold substrate. The streptavidin-coated, QD LBL assembled nanocomposites were captured on the gold substrate through biotin–streptavidin interactions. Subsequent electrochemical signals of the captured QDs upon acid dissolution provide quantitative information on the concentrations of Pb2+ with a dynamic range from 1 to 1000nM. Due to the dramatic signal amplification by the numerous QDs, subnanomolar level (0.6nM) of Pb2+ can be detected. The proposed sensor also shows good selectivity against other divalent metal ions and thus holds great potential for the construction of general DNAzyme-based sensing platform for the monitoring of other heavy metal ions.

Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces

This study examines the adsorption isotherms, kinetics and mechanisms of Pb²(+) sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb²(+) in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb²(+) with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca²(+) and PO₄³⁻ concentrations during the metal sorption processes. The Pb²(+) sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb(+). The sorption isotherm results indicated that Pb²(+) sorption onto the Langmuir and Freundlich constant q(max) and K( F ) is 9.52 and 8.18 mg g⁻¹, respectively. Sorption kinetics results indicated that Pb²(+) sorption onto WCBP was pseudo-second-order rate constants K₂ was 1.12 g mg⁻¹ h⁻¹. The main mechanism is adsorption or surface complexation (≡POPb(+): 61.6%), co-precipitation or ion exchange [Ca₃(.)₉₃ Pb₁(.)₀₇ (PO₄)₃ (OH): 21.4%] and other precipitation [Pb 50 mg L⁻¹ and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb²(+) removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb²(+) indicates its potential as another promising way to remediate Pb²(+)-contaminated media.

Biosorption of lead by E. coli strains expressingVitreoscilla hemoglobin: Isotherm modeling with two‐and three‐parameter models

AbstractBiosorption is presented as an alternative choice to traditional physicochemical means for removing toxic metals from groundwater and wastewaters. Removal of lead (Pb) from solutions was studied using Escherichia coli (parental) and Vitreoscilla hemoglobin (VHb)‐expressing E. coli (transformed) cells. Pb biosorption was increased in bacterial hemoglobin‐expressing E. coli cells grown in Luria broth B containing different concentrations of Pb2+. The maximum Pb2+ biosorption of transformed and parental cells was determined to be 612 and 370 μg Pb/g biomass, respectively. The inhibitory effect of Pb2+ on the parental strain was determined at 10 ppm. However, in transformed cells, Pb2+ was lethal at 100 ppm. The optimum aeration required for the transformed cells was lower than that for the parental strain on a growth yield basis. A linear correlation was established between the biosorption and uptake amounts. The biosorption process was analyzed using two‐parameter (Langmuir, Freundlich, Temkin) and three‐parameter models (Sips, Redlich–Peterson, Toth). The chi‐square test was used to compare these models. It was demonstrated that the three‐parameter model is better in describing biosorption equilibria a, white the Sips equation showed the best description for both types of cells.

Effects of lead and pesticides on δ-aminolevulinic acid dehydratase of ring doves (Streptopelia risoria)

The effects of lead (Pb2+) and various pesticides on δ-aminolevulinic acid dehydratase (ALA-d) in avian blood, liver and kidney were studied. In blood, virtually all of the ALA-d activity was localized in the cellular fraction. Complete inhibition of RBC ALA-d occurred at an in vitro Pb2+ concentration of ∼10 μmol/g protein, with an IC50 of ∼0.9 μmol/g protein. Pesticides (carbaryl, carbofuran, chlorpyrifos, diazinon, dieldrin, fenitrothion, hexachlorobenzene) added to blood samples up to 10 mM in vitro had no inhibitory effect on ALA-d, nor did the presence of pesticides greatly modify the response of ALA-d to inhibition by increasing concentrations of Pb2+. Recovery of Pb-inactivated RBC ALA-d activity was accomplished by treatment of blood hemolysates with Zn2+ and an SH-reducing agent such as dithiothreitol (DTT). A combination of Zn2+ (4 mM) and DTT (120 mM) was required to achieve complete recovery of Pb-inhibited enzyme activity. Normal avian ALA-d activity was greatest in blood, followed by liver, then kidney. Unlike blood hemolysates, liver and kidney homogenates contained a fraction of ALA-d activity which was very resistant to inhibition by in vitro Pb2+. In vivo, hepatic ALA-d was unaffected by Pb exposure (2.5 μg Pb2+/g body weight injected intraperitoneally), but renal ALA-d was decreased as a result of greater deposition of Pb in kidney than in liver. Inhibition of ALA-d in avian blood, particularly when expressed as a ratio of fully restored:nonrestored activity (activity ratio), is a highly specific, sensitive indicator of Pb exposure, deposition and corresponding enzyme inhibition in other target organs (kidney).

Fractal-like adsorption kinetics of Pb2+ in rocks

The adsorption kinetics of Pb2+ in rocks has been studied using ion selective electrodes and atomic absorption spectrophotometer. The results showed that the adsorption process is a fractal-like reaction. The adsorption rate was relatively high before 30 minutes, and then dropped. The saturated adsorption capacity (a) of Pb2+ and kinetic parameters (b, a, D and k) increased with increasing initial concentrations of Pb2+. These parameters (except a) decreased while Na+ was present in the solution. Furthermore, the smaller the rocks were in grain size, the bigger these kinetic parameters would be, though the parameter a was almost constant.

Effect of Pb-ions on the kinetics of devitrification and viscosities of AlF3-based glasses for waveguide fabrication

Aluminium fluoride glasses doped with different concentrations of Pb2+ have been analyzed for their devitrification characteristics. The kinetics of devitrification, using isothermal and non-isothermal calorimetric techniques, were studied for PbF2-containing glass compositions: 99-x99(39AlF3–6MgF2–22CaF2–6SrF2–6BaF2–10LiF–8NaF–2NaPO3)–xPbF2–1NdF3, in which the concentrations of PbF2 were varied between 0.34mol% and 15mol%. Based on the kinetics of devitrification, we comment on the thermal stability of PbF2-containing fluoroaluminate glasses.

Crystallization of PbxSr1-x(NO3)2 Solid Solutions from Aqueous Solutions

A series of PbxPr1-x(NO3)(2) crystals have been grown from aqueous solutions and characterized by X-ray powder diffraction. All diffraction data were well indexed according to the simple cubic structure. The variation of lattice constants with the concentrations of Pb2+ in the crystals accorded quite well to the Vegard's Law. The composition of the Sr(NO,), crystal doped with Pb2+ was studied by electron microprobe and it was found that Pb2+ was enriched in the 111 sectors. Equilibrium behavior in the Pb(NO3)(2)-Sr(NO3)(2)-H2O system was analyzed by Lippmann's phase diagram and the equilibrium distribution coefficient D-ph = 133.6. This large value of D indicates that Pb2+ ion is preferentially distributed to the solid phase.

Development of a simplified model of dynamic exchange of cations in a thin layer of zeolite. Part 1. Exchange of Pb2+ ions from solution with Na+ ions from thin layers of zeolite A

A model of the kinetics of a dynamic exchange of cations in solution with cations from thin layers of zeolite(s) is developed. The validity of the model is confirmed by the correlation between measured and calculated values of the concentrations of Pb2+ ions in both the layers of zeolite A and the lead nitrate solutions passed through the layers of zeolite A. For this purpose, the initial concentration of Pb2+ ions in the solutions, the mass of zeolite A in the layer and the flow rate of the solution through the layers of zeolite A were varied.

Lead and mercury mutagenesis: Role of H2O2, superoxide dismutase, and xanthine oxidase

It has been suggested that reactive oxygen intermediates (ROIs) may have a role in the genotoxic effects of lead (Pb2+) and mercury (Hg2+), but there have not been any definitive studies demonstrating a causal relationship between the induction of ROIs by these metals and mutagenesis. We previously demonstrated, using the transgenic Chinese hamster ovary cell line AS52, that low concentrations (0.1-1 microM) of Pb2+ and Hg2+ are mutagenic. In the present study, using a novel histochemical computer-enhanced image analysis technique, we demonstrate that Pb2+ and Hg2+ induce the formation of H2O2 in AS52 cells by at least two distinct mechanisms. One is characterized by the rapid induction of H2O2 following treatment of cells with concentrations of Pb2+ or Hg2+ below 0.8 and 1 microM, respectively, while the second occurs in AS52 cells treated with concentrations of Pb2+ or Hg2+ greater than 0.8 and 1 microM, respectively. Pb2+ and Hg2+ (0.1-1 microM) had no effect on the activities of partially purified catalase, glutathione peroxidase, or glutathione reductase, important enzymes involved with antioxidant defense, but these metals stimulated the activities of copper-zinc superoxide dismutase (CuZn-SOD) and xanthine oxidase (XO). Allopurinol (50 microM), a specific inhibitor of xanthine oxidase, inhibited the induction of H2O2 by Pb2+ (0.8-1 microM) and Hg2+ (1 microM) and also inhibited Pb2+- and Hg2+-induced mutagenesis. These results demonstrate that Pb2+ and Hg2+ disrupt the redox status of AS52 cells by enhancing the activities of CuZn-SOD and XO. Furthermore, the results of these studies also demonstrate that there is a causal relationship between the induction of H2O2 by these metals and mutagenesis.

The Silver Electrode in Square-Wave Anodic Stripping Voltammetry. Determination of Pb2+ without Removal of Oxygen

A silver rotating disk electrode is used for the determination of lead in concentrations from 2 × 10-9 to 3 × 10-7 M by square-wave anodic stripping voltammetry (SWASV) without removal of oxygen. The repeatability of consecutive SWASV runs in synthetic solutions covering the entire concentration range is better than 2%. The calibration curve is represented by a correlation coefficient of at least 0.999. The detection limit for a 2-min electrodeposition is 0.5 nM. Up to 600 runs can be carried out on synthetic solutions without any pretreatment of the electrode. A 4-fold excess of Cd2+ and a 10 000-fold excess of Cu2+ do not interfere with the determination of part-per-billion concentrations of Pb2+. Surfactants present in tap water distort the SWASV. Improvement of the analytical response in tap water is achieved by pretreatment of the samples: irradiation at 254 nm or digestion with HNO3. During anodic stripping voltammetry in the concentration range studied, a uniformly distributed submonolayer of lead, occupying 0.02%−1% of the real surface of the electrode, is formed by underpotential deposition. Linearity in calibration plot is achieved up to 1% electrode coverage; in terms of the experimental parameters of the deposition step (rate of rotation and time of electrolysis), this condition for linearity is CPb2+N1/2td ≤ 2.2 × 105 nM rpm1/2 s.

Lead Alters Growth and Reduces Angiotensin II Receptor Density of Rat Aortic Smooth Muscle Cells

Environmental lead (Pb2+) contributes a small but significant risk to human hypertension. It is postulated that the hypertensinogenic action of Pb2+ may be due, in part, to its direct action on vascular smooth muscle cells. To investigate this hypothesis, freshly isolated rat aortic smooth muscle (RASM) cells were propagated in defined media containing one of two Centers for Disease Control-based concentrations of Pb2+ (as lead citrate): 100 and 500 micrograms Pb2+/l (i.e., equivalent to 5.5 and 27.5 micrograms Pb2+/dl blood; designated 100-RASM and 500-RASM). Control (CON-RASM) cells received sodium citrate. 500-RASM cells exhibited suppressed propagation and fell out of propagation synchrony with CON-RASM cells: when CON-RASM cell approached confluence (approximately 90%), 500-RASM cell density was 6.4% that of CON-RASM cell density. By contrast, 100-RASM cells exhibited marked hyperplasia albeit this was not apparent until passage 3 (p3). Overall, when p3-p6 CON-RASM cells approached confluence, 100-RASM cell density was 107.6% greater than CON-RASM cell density. The protein content of CON-RASM and 100-RASM was not different, whereas that of 500-RASM cells was 29% greater than that of CON-RASM and 100-RASM cells. Phase-contrast microscopy revealed that 100 micrograms Pb2+/l converted normal spindle-shaped/ribbon-shaped RASM cells into less spread, cobblestone-shaped, neointimal-like cells. Immunocytochemical analysis revealed that 100-RASM cells lacked or had markedly fewer actin cables, characteristic of rapidly dividing cells. In addition, Pb(2+)-treated RASM cells exhibited altered membrane fatty acyl composition with a trend towards an increase (by as much as 50%) in membrane arachidonic acid. Interestingly, hyperplastic 100-RASM cells exhibited a 70.6% reduction in angiotensin II (Ang II) receptor concentration whereas the concentrations of alpha 1- and beta-adrenergic and atrial natriuretic peptide (ANP) receptors were not affected. In addition, in experiments designed to control for Pb(2+)-associated differences in RASM cell propagation, there was a concentration-dependent decrease in Ang II receptor concentration: for 100 and 500 micrograms Pb2+/l, Ang II receptor concentration was decreased 39.6% and 65.5%, respectively. Thus, although Pb2+, depending on its concentration, had contrasting effects on RASM cell propagation, it had a consistent, concentration-dependent inhibitory effect on Ang II receptor concentration. Recovery (r) from Pb2+ required at least two additional passages. At p71r the enhanced propagation (+54%) and reduced Ang II receptor concentration (-49%) of 100r-RASM cells persisted.(ABSTRACT TRUNCATED AT 400 WORDS)