Protective effects of DL-alpha-lipoic acid on cadmium-induced deterioration of rat hepatocytes

The suitability of DL-alpha-lipoic acid (LA) to serve as an antidote in cadmium (Cd) toxicity in rat hepatocytes was investigated. Isolated hepatocytes were exposed to 200 and 450 microM Cd in the presence of 0.2, 1.0 and 5.0 mM LA, respectively. After 30 min of incubation various criteria of cell viability were monitored. Lipoic acid markedly diminished Cd uptake. Concomitantly, Cd-induced membrane injury, as reflected by the leakage of aspartate aminotransferase and sorbitol dehydrogenase (SDH) was decreased. Moreover, LA protected against intracellular toxic responses to Cd, such as a decrease in cellular SDH activity, a decrease in cellular acid soluble thiols, especially in total glutathione, a decrease in cellular urea and an increase in thiobarbituric acid (TBA) reactants, as a measure of lipid peroxidation. Most protective effects were seen in hepatocytes challenged with the lower Cd concentration and coincubated with 5 mM LA. In contrast, at 450 microM Cd even the highest LA concentration applied either did only reverse Cd-effects incompletely (SDH-response, TBA-reactants) or did not protect at all (Cd uptake, enzyme leakage, loss of glutathione). The data indicate that DL-alpha-lipoic acid serves as a protective tool against Cd-induced membrane damage and cell dysfunction in hepatocytes. This stands as long as Cd exposure is low enough to permit interaction with LA prior to interaction with cell structures.     

Relative in vitro affinity of hepatic metallothionein for metals

The ability of selected metals (Ag, Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Tl and V) to displace Zn from Zn-metallothionein (Zn-MT) was quantitated. Of the metals tested Cd had the highest affinity for MT, with 1.33 microM displacing 50% of the 65Zn bound to MT (EC50), followed by Pb (1.46 microM), Cu (1.93 microM), Hg (3.93 microM), Zn (8.06 microM), Ag (10.4 microM), Ni (474 microM) and Co (880 microM). As, Ca and Mo had a limited ability to displace Zn from MT while Al, Cr, Fe, Mg, Mn, Tl and V had no effect on Zn binding even at 1.0 mM.     

Cadmium-induced renal lipid peroxidation in rats and protection by selenium.

Cadmium has been recognized as one of the most toxic environmental and industrial pollutants. The kidney is a critical target organ following Cd exposure. The aim of this study was to investigate the effects of cadmium-induced peroxidative damage to rat kidney. Treatment of rats with Cd resulted in a time- and dose-related accumulation of metal in kidney. Cd produced enhanced lipid peroxidation in plasma and kidney. These Cd-induced changes were accompanied by a significant rise in renal Fe and Cu, and a fall in tissue Zn and Se. Concurrent treatment with Se and Cd reduced the Cd-induced alterations in renal peroxidation and essential metal levels. Data suggest that lipid peroxidation is associated with Cd toxicity and that Se was found effective in attenuation of these renal effects.     

CADMIUM-INDUCED RENAL LIPID PEROXIDATION IN RATS AND PROTECTION BY SELENIUM

Cadmium has been recognized as one of the most toxic environmental and industrial pollutants. The kidney is a critical target organ following Cd exposure. The aim of this study was to investigate the effects of cadmium-induced peroxidative damage to rat kidney. Treatment of rats with Cd resulted in a time- and dose-related accumulation of metal in kidney. Cd produced enhanced lipid peroxidation in plasma and kidney. These Cd-induced changes were accompanied by a significant rise in renal Fe and Cu, and a fall in tissue Zn and Se. Concurrent treatment with Se and Cd reduced the Cd-induced alterations in renal peroxidation and essential metal levels. Data suggest that lipid peroxidation is associated with Cd toxicity and that Se was found effective in attenuation of these renal effects.     

Involvement of cardiac metallothionein in prevention of adriamycin induced lipid peroxidation in the heart

The effect of pretreatment of mice with heavy metals: Zn, Cu, Bi, Co, Cd or Hg, against lethal and cardiac toxicity of adriamycin (ADR) was investigated. The lethal toxicity of ADR was significantly reduced by pre-administration of these metals except for Cu. The levels of both malondialdehyde and conjugated dienes, determined as indicators of lipid peroxidation in the heart, markedly increased with ADR administration, but the increases were significantly prevented by the pre-administration of Zn, Bi or Cd. The survival rate of mice after ADR injection was significantly correlated with metallothionein (MT) levels in the hearts which was increased by the injection of each metal, but was not correlated with those in the liver and kidneys. A significant negative correlation between the cardiac MT concentrations and the levels of lipid peroxidation in the hearts was also observed. These results suggest that increased MT synthesis in the heart may be involved in the protective effect of the heavy metals tested against the lethal and cardiac toxicities of ADR.     

ICP-AES/ICP-MS测定西藏和河南产藏红花中主要金属元素及重金属含量(英文)

建立了ICP-AES/ICP-MS测定西藏和河南产藏红花中19种元素含量的方法。19种元素包括主要元素Ca、Fe、Mg、P、Sr、Al、Mn、Zn、V、Cr、Se、Co、Ni、Mo和重金属As、Cu、Cd、Hg、Pb。对于所测元素,标准曲线的相关系数>0.9938,方法的相对标准偏差RSD<5.25%。结果表明,ICP-AES/ICP-MS可用于藏红花质量控制,并为西藏和河南产藏红花中元素的含量测定提供了方法。     

Effects of certain mono-, di- and trivalent metal cations on the K+-stimulated p-Nitrophenyl phosphatase in rat brain

The effects of certain monovalent (Ag+1 and Li+1), divalent (Hg+2, Cu+2, Zn+2, Co+2, Fe+2, Pb+2, Mn+2, Sn+2, Ni+2, and Se+2) and trivalent (Fe+3, As+3, and Al+3) metals on a mitochondrial preparation of K+-stimulated-p-nitrophenyl phosphatase (K+-PNPPase) from rat brain were studied. Except for salts of Ni+2, Se+2 and Li+1, which irrespective of concentration failed to produce 50% inhibition, all of the metals examined were found to be potent inhibitors of the enzyme with 150 values of 0.24 microM for Ag+1 among the monovalent, 0.70, 30, 37, 38, 47, 60, 62, 490 and 850 microM for Hg+2, Cu+2, Cd+2, Zn+2, Co+2, Fe+2, Pb+2, Mn+2 and Sn+2, respectively, among the divalents and 100, 550 and 870 microM for Fe+3, As+3, and AL+3 respectively, among the trivalents. Salts of silver and mercury were the most toxic for this enzyme. All metals showed concentration dependent inhibition except lithium. The order of their potency was Ag+1 greater than Hg+2 greater than Cu+2 greater than Cd+2 greater than Zn+2 greater than Co+2 greater than Fe+2 greater than Pb+2 greater than Fe+3 greater than Mn+2 greater than As+3 greater than Sn+2 greater than Al+3 greater than Ni+2 greater than Se+2 greater than Li+1.     

Cadmium and mercury accumulation in rat hepatocytes: interactions with other metal ions.

The uptake of essential metals, such as calcium, copper (Cu), iron (Fe), and zinc (Zn), occurs through processes that include energy-independent carrier mechanisms as well as ion channels. Since cadmium (Cd) and mercury (Hg) inhibit the uptake of these metals, this study examined whether the essential metals in turn affect Cd and Hg accumulation. The uptake of 3 microM Cd was inhibited by Cu, Fe, Zn, and Hg, with 100 microM Zn having the greatest effect. Kinetic analysis indicated that these metals inhibited Cd accumulation in a competitive manner. In comparison, neither the essential metals nor Cd had any significant effect on Hg accumulation. At 4 degrees C the accumulation of Cd was reduced to 20% of that at 37 degrees C, while Hg uptake remained unaffected. The efflux of Cd from the hepatocytes was biphasic, energy-independent, and not affected by Zn, Cu, or Fe. Thus the essential metals decreased Cd accumulation by inhibiting its uptake. On the other hand, Hg decreased Cd accumulation by both inhibiting its uptake and enhancing its efflux. As determined by the organic SH blockers, nearly two-thirds of the Cd entered the hepatocytes through processes involving the SH ligands. The uptake of Hg, however, was not affected by the SH blockers. Furthermore, the fraction of membrane-bound Hg at 3 microM concentration was 2.5 times greater than Cd, indicating that Hg is associated with additional binding sites not utilized by Cd. These results suggest that in hepatocytes Cd uptake occurs mainly through the SH-containing transport processes associated with the uptake of Zn and, to a smaller extent, Cu and Fe. Hg can inhibit Cd uptake by binding to these sites; however, its own uptake occurs via other processes that remain to be elucidated.     

Lack of protection against chemically induced injury to isolated hepatocytes by omission of calcium from the incubation medium

Recent evidence has renewed interest in the hypothesis that Ca plays a central role in cell death. It was previously found that Cd and CuCl2 cause loss of viability of isolated hepatocytes. It was therefore of interest to determine whether Ca was intimately involved with the toxic effect of these metals. Some of the chemicals that were previously shown to be toxic through a mechanism involving Ca (amphotericin B, lysolecithin, and Ca ionophore A23187) were also included in the study. Hepatocytes were incubated with one of these chemicals and samples taken at various time points up to 120 min for estimation of cell viability (intracellular K+ and leakage of aspartate aminotransferase) and lipid peroxidation. The toxic effects due to Cd or Cu were not ameliorated on omission of Ca from the incubation medium. Furthermore, of the other three chemicals investigated, only the toxic properties of the Ca ionophore were effectively blocked by incubation in a Ca-free medium. The results of this study do not support the hypothesis that Ca plays a ubiquitous role in the death of liver cells.     

A study on metals content in patients with colorectal polyps

Data on metals involvement in colorectal polyps are scarce and fragmentary. The aim of this study was to examine whether the level of metals could be associated with risk of colorectal polyp development. The concentration of 15 chemical elements (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg Mg, Mn, Pb, Se, Sr, and Zn) in 17 colorectal biopsies of healthy individuals, in 15 polypotic and corresponding nonpolypotic biopsies taken from the same individual, was evaluated. Concentration in polyps of metals such as Al, Ca, Mg, Mn, Pb, Sr, and Zn was unchanged both in unpaired and paired samples; elements such as Ba, Cd, and Hg were significantly lower and Fe was significantly higher both in individual and paired tissues. Cobalt, Cr, and Cu were significantly different only between polyps and the adjacent normal tissue area; Se showed a significant accumulation comparing polyps versus healthy tissues. The difference found in some elements between polyps and a control tissue provides an indication about the role of essential and nonessential elements in the early stage (polyps) in the colon carcinogenic process and encourages further studies to confirm the involvement of such elements in neoplastic processes.     

不同产地当归中金属微量元素的比较研究

目的：对不同产地当归中金属微量元素的含量进行初步的比较研究。方法：样品经微波消解后,以铟（In）元素为内标,利用电感耦合等离子体质谱（ICP-MS）测定不同产地的当归中Be、B、A l、V、Cr、Mn、Fe、Co、N i、Cu、Zn、As、Se、Cd、Ba、Hg和Pb等17种微量金属元素的含量。结果：该方法对各元素的检测线为0.003~2.478 ng/g,加样回收率为82.3%~112.2%,标准物质杨树叶的测定值与标示量基本吻合。结论：所建立的方法快捷,准确、灵敏度高,可以用于测定当归中金属的微量元素的含量,不同产地的当归其所含金属微量元素有很大不同,如某地产的当归有些元素含量明显高于其他地方。     

中药马齿苋的微量元素测定

本文报道用原子吸收分光光度法及等离子体发射光谱法测定马齿苋中二十一种微量元素的结果。     

Dose-response effects of various metal ions on rat liver metallothionein,glutathione, heme oxygenase,and cytochrome P-450

Adult male rats received ip injections of the maximum tolerable dose (MTD; μmol/kg/day, in parentheses following metal), or a fraction thereof, of Hg (5), Cd (20), Se (25), Ag (65), Cu (75), Co (100), Ni (120), Zn (200), Mn (250), Fe (300), Pb (400), or Cr (400) 36 and 12 hr before sacrifice. MTDs were estimated from previous studies, and at least three serial dilutions ($\text{1}\text{2}$, $\text{1}\text{4}$, $\text{1}\text{8}$, etc.) of the MTDs were tested for each metal. The effects of metal treatment on hepatic heme oxygenase activity (HO), cytochrome P-450, reduced glutathione (GSH) and metallothionein (MT), and renal MT and GSH were determined. Nine metals increased HO at the MTD, but only Cd, Se, Mn, and Pb increased HO at lower doses. These four metals plus Ag and Cr depressed cytochrome P-450 levels at the MTD, but only Cd, Mn, and Pb depressed cytochrome P-450 at a lower dose. Se increased hepatic GSH at the two highest doses, but all other metals had little or no effect. Kidney GSH was increased by all metals except Cd, Ag, Cu, and Cr, to a maximum level of only 150% of control (Pb). Cd and Zn induced hepatic MT in a dose-related manner to 420 and 580% of control, respectively. On a molar basis, Cd was about eight times more potent than Zn in increasing hepatic MT concentration. Hg, Ni, Mn, Fe, Pb, and Cr also significantly increased hepatic MT, but only to 150–200% of control. Pb had a slight but significant effect on hepatic MT at all doses down to 1/16th the MTD. This effect of PB, as well as other metals having a small effect on MT, may be the result of the effects of stress on MT rather than the metal ion per se. Renal MT was effectively induced by Hg, Cd, Cu, Ni, Zn, and Pb. Relatively small amounts of Hg (0.62 μmol/kg/day) significantly increased renal MT when compared to the minimum effective dose of Cd (10 μmol/kg/day) or Zn (50 μmol/kg/day). In conclusion, metals have a number of effects on potential hepatic and renal biochemical defense mechanisms. Most of the metals lacked specificity, affecting a number but not all of the parameters examined. However, of the 12 metals examined, Zn was the most selective in that it produced marked increases in MT and little or no effect on the other parameters, whereas Cd had the broadest effect, altering all parameters except GSH.     

The effect of cadmium and other metals on vascular smooth muscle of the dogfish shark, Squalus acanthias

The effect of Cd2+ and related metals (Ni2+, Hg2+, Pb2+, Co2+, Sn2+ Cu2+ and Zn2+) on vascular tension was studied using isolated rings of endothelium-free, smooth muscle from the ventral aorta of the shark, Squalus acanthias. Both Cd2+ and Ni2+ produced significant vasoconstriction at concentrations at or above 10(-6) M (112 and 59 ppb, respectively); the other metals were either marginally constrictive (Hg2+ and Sn2+) or were without effect (Pb2+, Co2+, Cu2+, and Zn2+). We suggest that previously published vascular effects of Hg2+ and Pb2+ may have been secondary to responses of the vascular endothelium, and that the role of Ni2+ in hypertension should be investigated further. Our data indicate that the effects of metals on this vascular smooth muscle are specific and not generic. Moreover, this system could be utilized to investigate the mechanisms of metal-induced vasoconstriction.     

Effects of various trace metals on the binding of cadmium to rat hepatic metallothionein determined by the Cd/hemoglobin affinity assay

The Cd/hemoglobin affinity assay is finding increasing use as an indicator of metallothionein in a variety of biological tissues. Because the assay relies on the ability of heat-stable proteins to bind Cd, it is important to know the relative affinities of different trace metals to bind to such proteins, relative to Cd. This study examines the ability of 15 trace metals to prevent the binding of Cd to metallothionein using the Cd/hemoglobin affinity assay for metallothionein. Cd, Cu, Hg, and Ag were the only metals tested which significantly inhibited the binding of a fixed concentration (2 microM) of 109Cd to a crude preparation of rat hepatic metallothionein. As, Co, Cr, Fe, Mn, Mo, Ni, Pb, Sn, Th, and Zn had no inhibitory effect at the highest concentrations tested. However, As, Sn, Th, and Zn prevented the precipitation of hemoglobin at relatively low concentrations and, thus, could not be fully tested for inhibitory potency. Cu was the most potent inhibitor, producing more than 90% inhibition at 5 microM, followed by Ag, Hg, and Cd, which produced 76, 72, and 65% inhibition of cadmium binding at 5 microM, respectively. These results suggest that caution should be taken in interpreting metallothionein concentrations obtained by the Cd/hemoglobin affinity assay in tissues which contain relatively a high concentration of Cu, Ag, or Hg, relative to that of Cd.     

Translational responses and oxidative stress of mussels experimentally exposed to Hg, Cu and Cd: one pattern does not fit at all

Certain metals, like Hg, Cu and Cd, are capable of down-regulating protein synthesis in several marine organisms, including Mytilus galloprovincialis. Nevertheless, due to the complexity of the environmental stress, it is difficult to evaluate the influence of individual metals on protein synthesis via field studies. To bypass this difficulty, experimental studies were carried out on M. galloprovincialis exposed in aquarium for 15 days to one of three selected metal salts, HgCl(2), CuCl(2) and CdCl(2). Polysome profile was determined in digestive gland extracts of the exposed mussels as a way of measuring the functional status of ribosomes, superoxide radical production and lipid peroxidation as indicators of oxidative stress, metallothionein content as a metal detoxification index, and superoxide dismutase activity as a free radicals-scavenging index. Exposure of mussels to Hg(2+) or Cu(2+) resulted in a concentration- and time-dependent decrease in the polysome content of digestive gland cells, which at 15th day of exposure and at the highest metal concentrations tested, was 32% and 19% of the control, respectively. Both metals, at the concentrations used (<40 μg/L), did not significantly influence the oxidative stress biomarkers. By contrast, Cd(2+) treatment significantly induced superoxide radical production and lipid peroxidation in digestive gland cells, hinting that mussels suffered from oxidative stress. Polysome levels in Cd(2+)-exposed mussels were initially decreased by day 5 in digestive gland cells and then elevated to reach nearly the control levels by 15 days of exposure. Elevated protein synthesis was associated with significantly increased production of metallothioneins, whereas such increase was not recorded in Hg(2+)- or Cu(2+)-exposed mussels. Interestingly, the ribosome efficiency at initiating protein synthesis followed a similar pattern of polysome alterations, a fact suggesting that regulation of protein synthesis mainly occurred at the initiation phase of translation. Overall, these results suggest that the effect of each metal on protein synthesis is idiosyncratic and depends on its ability to induce specific cellular defense mechanisms against oxidative stress.     

CCl4-induced lipid peroxidation in isolated rat hepatocytes with different oxygen concentrations

It has been difficult to demonstrate convincingly the occurrence of lipid peroxidation by increases in the concentration of thiobarbituric acid (TBA) reactants in response to carbon tetrachloride (CCl₄) in hepatocytes isolated from fed, nontreated rats. This study was undertaken to determine whether or not the incubation atmosphere and the content of the incubation media could be contributing factors for the inhibition of CCl₄-induced lipid peroxidation. Isolated hepatocytes incubated in either Eagle's minimum essential medium (EMEM) or Tris buffer were incubated with and without CCl₄ (1 or 5 μl/4 ml hepatocyte suspension) under an atmosphere of either air or carbogen (95% O₂:5% CO₂). Samples were taken at 30, 60, or 120 min for determination of ethane (in the gas phase), TBA reactants concentration, and leakage of lactate dehydrogenase (LDH). Under air, CCl₄ stimulated ethane formation and increased the concentration of TBA reactants in hepatocytes isolated from fed, nontreated rats. This stimulatory effect was found irrespective of the incubation medium, although absolute values were generally lower in Tris buffer than in EMEM. Losses of LDH were also observed with the higher concentration of CCl₄. When carbogen was the atmosphere for incubation, no significant increases in the lipid peroxidation parameters could be found in response to CCl₄. Again, this response was irrespective of the incubation medium. Under carbogen, CCl₄-induced LDH leakage was no longer observed. Thus, these data provide a possible explanation as to why it has been difficult to observe lipid peroxidation, as evidenced by elevated TBA reactants concentration in hepatocytes isolated from fed, nontreated rats.     

Effects of phospholipase A2 inhibitors on diethyl maleate-induced lipid peroxidation and cellular injury in isolated rat hepatocytes

Isolated hepatocytes provide a suitable system for investigation of various aspects of the mechanism of a toxic response. The mechanism by which most chemicals induce hepatotoxicity is still not known. Evidence that phospholipases may play a role in cellular injury has been reported. In the present study the effects of reported inhibitors of phospholipase A2 (quinacrine, chlorpromazine, dexamethasone, and dibutyryl cyclic AMP) on diethyl maleate (DEM)-induced lipid peroxidation, reduced glutathione (GSH) depletion, and cellular injury were examined in isolated hepatocyte suspensions. Hepatocytes were incubated for 7 h under control conditions or with (1) DEM (4 mM), (2) one of the inhibitors (quinacrine, 10, 50, or 150 microM; chlorpromazine, 50 microM; dexamethasone, 0.1, 0.5, 1, or 2.5 mM; dibutyryl cyclic AMP, 0.1, 0.5, 1, or 2.5 mM) or aspirin (500 microM), or (3) a combination of DEM and one of the inhibitors or aspirin to determine their effect on DEM toxicity. Samples were withdrawn at hourly intervals for estimation of cellular injury (loss of intracellular K+ and lactate dehydrogenase and trypan blue exclusion index), lipid peroxidation (thiobarbituric acid reactants assay), and GSH concentration. Quinacrine and chlorpromazine inhibited DEM-induced lipid peroxidation but not cellular injury or GSH loss. This suggests that phospholipase A2 may be involved in DEM-induced lipid peroxidation but not cell damage. However, dexamethasone and dibutyryl cyclic AMP enhanced both lipid peroxidation and loss of cell viability due to DEM, suggesting novel aspects of the biochemical mechanisms of chemically induced cytotoxicity.     

Pharmacological characterization of Aristolochia clematitis L. growing in the Stavropol Region

The amino acid and elemental composition of birthwort (Aristolochia clematitis L.) plant species occurring in the Stavropol region has been studied. The analyses showed a high content of tyrosine in the above-ground parts and revealed the presence of 25 elements (K, Ca, P, Mg, Al, Fe, Na, Si, Mn, Zn, Cu, Ni, Cr, V, Li, As, Pb, Co, J, Se, Cd, Hg, Be, Sn, Ti), some of which belong to the group of toxic metals. The differentiation of various plant organs with respect to the accumulation of different groups of chemical elements is established. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 4, pp. 23–24, April, 2006.