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.     

Concentration of Metallothionein in Major Organs of Rats after Administration of Various Metals

Concentration of Metallothionein in Major Organs of Rats afterAdministration of Various Metals. WAALKES, M. P., AND KLAASSEN,C. D. (1985) Fundam. Appl. Toxicol. 5, 473–477. The effectof various metals (Cd, Cr, Fe, Pb, Mn, Hg, Ni, Zn) at maximumtolerated doses on metallothionein (MT) concentrations in majororgans (brain, heart, intestine, kidney, liver, lung, pancreas,spleen, stomach, and testes) of rats was measured by the Cd-radioassaytechnique. Zn produced the most dramatic changes in MT, increasingconcentrations 260-, 86-, 44-, and 14-fold over control forpancreas, intestine, liver, and kidney, respectively. Zn increasedMT in every organ examined except brain. Cd was also effectivein increasing MT levels, elevating concentrations in all organsexcept brain and testes. Testes was the only organ in whicha metal decreased MT levels, where Cd produced a 90% decrease.Cr, Fe, Pb, and Mn increased MT concentrations only in hepatictissue, while Hg and Ni increased MT in liver, kidney, and pancreas.Results indicate that Zn is the most effective inducer of MTsynthesis in several tissues and that liver appears to be themost responsive organ to increased MT synthesis following exposureto a number of metals     

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.     

Protective effect of metallothionein inducing metals on lethal toxicity of cis-diamminedichloroplatinum in mice

A protective effect of preadministration of the metals Cu, Bi, Zn, Hg, Cd, Ni or Co, against lethal toxicity of cis-diamminedichloroplatinum (Cisplatin; CDDP) was observed in mice. However, the protective effect seems not always to correlate with metallothionein (MT) levels in the liver and kidney of mice treated with one of these metals, suggesting possible participation in this protection of mechanisms other than MT induction by the preadministered metals.     

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.     

The protective effect of metallothionein on the toxicity of various metals in rat primary hepatocyte culture

Metallothionein (MT), a low-molecular-weight, cysteine-rich, metal-binding protein, has been implicated in the detoxification of Cd. However, whether MT protects against the cellular toxicity of other metals has not been examined thoroughly. This study was therefore designed to determine the effects of Zn-induced MT on the toxicity of seven metals in rat primary hepatocyte cultures. Hepatocytes were grown in monolayer culture for 22 hr and subsequently treated with ZnCl2 (100 microM) for 24 hr which produced a 15-fold increase in MT concentration. Following Zn pretreatment, hepatocytes were exposed to various concentrations of Ag, Co, Cu, Hg, Ni, Pb, or Zn for 24 hr. Cytotoxicity was assessed by enzyme leakage and loss of intracellular K+. The toxicity of all seven metals was significantly less in the Zn-pretreated cells. Zn pretreatment had no appreciable effect on the hepatocellular uptake (1-24 hr) of 110Ag or 203Hg, but markedly altered their subcellular distribution, with metals accumulating more in the cytosol and less in the nuclear, mitochondrial, and microsomal fractions. In the cytosol of control cells, the metals were bound mainly to high-molecular-weight proteins whereas in the Zn-pretreated cells, the metals were mainly associated with MT. In summary, Zn-induced MT in rat primary hepatocyte cultures protects against Ag-, Co-, Cu-, Hg-, Ni-, Pb-, and Zn-induced cytotoxicity. This protection appears to be due to the binding of metals to MT with a concomitant reduction of metal content in critical organelles and proteins.     

Heavy metals in soil, vegetables and fruits in the endemic upper gastrointestinal cancer region of Turkey

The environmental exposure to heavy metals is a well-known risk factor for cancer. We investigated levels of seven different heavy metals, (Co, Cd, Pb, Zn, Mn, Ni and Cu) in soil, fruit and vegetable samples of Van region in Eastern Turkey where upper gastrointestinal (GI) cancers are endemic. Heavy metal contents of the samples were determined by flame atomic absorption spectrometer. Four heavy metals (Cd, Pb, Cu and Co) were present in 2- to 50-fold higher concentrations whereas zinc levels were present in 40-fold lower concentrations in soil. The fruit and vegetable samples were found to contain 3.5- to 340-fold higher amounts of the six heavy metals (Co, Cd, Pb, Mn, Ni and Cu) tested. The volcanic soil, fruit and vegetable samples contain potentially carcinogenic heavy metals in such a high levels that these elements could be related to the high prevalence of upper GI cancer rates in Van region.     

Induction of metallothionein by steroids in rat primary hepatocyte cultures

The purpose of this study was to characterize the induction of metallothionein (MT) by steroids in rat primary hepatocyte cultures. Comparison of the characteristics of MT induction by a steroid (dexamethasone) to that by metals (Zn and Cd), examination of the involvement of the glucocorticoid receptor in the steroid induction of MT, and determination of the potency and effectiveness of a number of steroids were studied. In general, the patterns of MT induction by metals and steroids were quite different. For metals, the maximal MT induction (12- to 39-fold) was limited by toxicity whereas for steroids, a plateau in MT induction (fivefold) occurred at noncytotoxic concentrations. Steroids elicited an increase in MT at concentrations that were one-hundredth to one-thousandth less than that of metals. A combination of metal and steroid increased the induction of MT to a level higher than achieved by metal or steroid alone. The effectiveness of steroids at inducing MT was related to their ability to induce a specific glucocorticoid effect, induction of tyrosine aminotransferase. For specific classes of steroids, synthetic glucocorticoids were more potent than the metals in inducing MT, but endogenous glucocorticoids, mineralocorticoids, androgens, and estrogens were less potent than the metals. The concentration of corticosterone, the major endogenous glucocorticoid of rats, required to induce MT in hepatocytes was 100 times higher than concentrations achievable in the plasma of rats. In conclusion, in rat hepatocytes dexamethasone was a more potent but less effective inducer of MT than Zn or Cd; synthetic glucocorticoids were more potent but endogenous adrenalcorticoids (i.e., glucocorticoids, mineralocorticoids, androgens, and estrogens) were both less potent and less effective inducers of MT than were metals, suggesting that glucocorticoids may not be the mediator for stress-induced MT induction; and induction of MT by steroids correlated well with the induction of tyrosine aminotransferase, supporting the involvement of a hormone-receptor complex in the induction of MT by steroids.     

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.     

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。     

The interaction of zinc and cadmium in the synthesis of hepatic metallothionein in rats

The interaction of injected zinc salts (Zn) and cadmium salts (Cd) with regard to the synthesis of metallothionein (MT) in adult rat liver was investigated. Male rats received an i.p. injection of Zn (20 mg/kg) or Cd (0.6 mg/kg) with or without pretreatment with Zn (20 mg/kg 16 h prior to the second injection). It was found that both metals, when administered singly, induced the synthesis of significant levels of hepatic MT, but that, when the Cd injection followed the Zn injection, synthesis of MT was not additive. When Zn pretreatment was followed by a second Zn injection, MT accumulation was additive (approx. 2-fold of that observed after a single Zn injection). Also, a highly significant positive correlation, (r = 0.97, P less than 0.01) was noted between hepatic Zn concentration and hepatic MT concentration, a relationship which was independent of the mode of MT induction. The results of the investigation indicate that: (1) in the presence of pre-existing hepatic Zn--MT, the ability of Cd to induce new MT synthesis is greatly reduced; rather, Cd is sequestered by the pre-existing MT; and (2) Zn may play a major role in the induction of MT synthesis both after Zn administration and after Cd administration.     

Assessment of environmental contamination using feathers of Bubulcus ibis L., as a biomonitor of heavy metal pollution, Pakistan

Concentrations of metals such as Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, Pb, and Zn were analyzed in the feathers of cattle egret (Bubulcus ibis) from three breeding colonies in the Punjab province, Pakistan. The mean concentrations of Ca, Cd, Fe, Pb and Mn were significantly different between the three study sites (River Chenab, River Ravi and Rawal Lake Reservoir). The mean concentrations of Ca, Cd, Fe and Mn were significantly greater at the River Chenab heronry and Cr, Co, Zn, and Pb concentrations at the River Ravi heronry. The feathers of cattle egrets collected from the Rawal Lake Reservoir heronry were least contaminated. Multivariate statistical methods viz., Factor Analysis based on Principal Component Analysis (FA/PCA); Hierarchical Cluster analyses (HACA), and Correlation Analyses identified relatively similar associations of metals and their sources of input. Metals such as Ca, Mg, and K were related with natural input from parent rock material whereas trace metals viz., Cu, Cd, Co, Pb, Ni, and Zn were associated mainly with anthropogenic processes. Metals such as Fe, Mn, and Li were either correlated with natural input or with anthropogenic activities. Concentration of heavy metals such as Cd, Pb, and Cr were well above the threshold level that can cause adverse effects in birds and pose menace to the cattle egrets population in Pakistan. The study suggested that the feathers of cattle egret could be used as a bio-monitor of the local heavy metals contamination.     

Evidence of species-specific detoxification processes for trace elements in shorebirds

This study investigated sub-lethal effects and detoxification processes activated in free-ranging Red Knots (RKs) (Calidris canutus) from the Pertuis Charentais on the Atlantic coast of France, and compared the results with previous data obtained on another shorebird species, the Black-tailed Godwit (Limosa limosa). The concentrations of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were assessed in the liver, kidneys, muscle and feathers. Stable isotope analyses of carbon and nitrogen were carried out to determine whether differences in diet explained variations in elemental uptake. The mRNA expression of relevant genes (cytochrome c oxidase 1, acetyl-CoA carboxylase, Cu/Zn and Mn superoxide dismutase, catalase, metallothionein, malic enzyme), antioxidant enzyme activities (catalase, glutathione peroxidase (GPx), superoxide dismutase), and metallothionein (MT) levels were investigated to shed light on trace element detoxification and toxic effects. Although Red Knots were characterized by elevated As and Se concentrations which were potentially toxic, most elements were usually below toxicity threshold levels. The results strongly suggested a dietary specialization of Red Knots, with individuals feeding on higher trophic status prey experiencing higher As, Hg and Se burdens. Red Knots and Godwits also showed discrepancies in elemental accumulation and detoxification processes. Higher As and Se concentrations in Red Knots enhanced catalase gene expression and enzyme activity, while Godwits had higher Ag, Cu, Fe and Zn levels and showed higher MT production and GPx activity. The results strongly suggest that detoxification pathways are essentially trace element- and species-specific.     

Hypothermia and hypometabolism: sensitive indices of whole-body toxicity following exposure to metallic salts in the mouse

To investigate the practicality of hypothermia and hypometabolism as sensitive indices of toxicity in the mouse, oxygen consumption was monitored continuously and body temperature was measured at 30 min postinjection following the intraperitoneal administration of various metal salts. Eleven metal ions were tested: Al3+, Cd2+, Co2+, Cr2+, Cu2+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+. All metals induced dose-dependent reductions in both oxygen consumption (hypometabolism) and deep body (colonic) temperature. Comparative toxicity of the metal ions was evaluated by calculating the dose of metal ion in dimensions of mmol/kg body mass needed to reduce colonic temperature to 35 degrees C. The order of toxicity from lowest to highest was as follows: Cr less than Al less than Pb less than Mn less than Mg less than Zn less than Cu less than Co less than Ni less than Hg less than Cd. The threshold doses for reducing body temperature were less than 5% of the LD50 in 6 of the metals studied. Metal salts with relatively low LD50 doses such as Hg, Cd, and Ni were most efficacious in inducing hypothermia and hypometabolism. Moreover, there was a direct linear relationship between dose for inducing hypothermia or hypometabolism and the reported LD50. Hence, the hypothermia and hypometabolism test may prove to be a sensitive and rapid test for the evaluation of toxicity of environmental contaminants.     

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.     

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.     

Inter-element interactions in human hair

The concentrations of 33 elements: Ca, Mg, Na, U, Cu, Zn, P, Fe, Mn, Cr, Se, B, Co, Mo, Si, V, Ni, Be, Hg, Cd, Al, Pb, As, Ba, Au, Pt, Ag, Sr, Sn, Ti, W, Sb and Zr in hair were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Hair samples (n=83) were collected between 1996 and 2003 from inhabitants of city of Wroc?aw, located in Lower Silesia, south-west Poland (urbanized and industrialized region). Inter-element interactions were studied by evaluation of correlation coefficients between two elements, as well as by multiple regression analysis. The strongest relations found between the elements in the hair were as follows: Mg and Ca, Mn and Ca, Sr and Ca, Sr and Mg, U and Na, Ni and Zn, Mn and Sr, Cd and Ni, Sb and Pt. We obtained also the following essential linear multiple dependences (p<0.05): Al=f(U, P, Mn), As=f(Zn, Fe) (Zn is negatively correlated, β<0), Cu=f(V), Fe=f(Mn, As), Mg=f(Ca), Ca=f(Mg, Ba), Ni=f(Zn, Cd), Sb=f(Pt, Sn, W) and Ti=f(Fe, Co). These relations can be useful in the explanation of relationships among the elements in man.     

Heavy metal concentration in muscle of pike (Esox lucius Linnaeus, 1758) from Anzali international wetland,southwest of the Caspian Sea and their consumption risk assessment

This study evaluated the concentrations of nine heavy metals in muscle specimens of pike (Esox lucius Linnaeus, 1758) from four sites of southwest of the Caspian Sea: Shijan, Abkenar, Hendakhale and Siakeshim. The potential human health risks due to consumption of pike have been assessed by estimated average daily intake (EDI) and target hazard quotient (THQ) of metals. In particular, Cu, Zn, Cd, Pb, Hg, As, Ni, Co and Mn were quantified in the edible tissue of specimens by AAS determination. The average metal concentrations of Cu, Zn, Cd, Pb, Hg, As, Ni, Co and Mn measured in this study were 1.12?±?0.264, 5.37?±?0.702, 0.058?±?0.023, 0.20?±?0.035, 0.005?±?0.002, 0.17?±?0.047, 0.33?±?0.062, 0.28?±?0.034 and 0.20?±?0.035?μg/g w wt, respectively. Our results demonstrate the consumption of muscle of pike for adult and children as less than 1, hence residents of these regions will not be exposed to significant health risks.     

Available intracellular Zn as a potential indicator of heavy metal exposure in rainbow trout hepatocytes

The measurement of available Zn in rainbow trout hepatocytes exposed to a selection of heavy metals was evaluated as a potential end point for assessing heavy metal exposure. Induction of metallothionein, a well-known biomarker for heavy metal exposure, was also evaluated concurrently with available Zn measurements. Rainbow trout hepatocytes were exposed to several concentrations of copper, cadmium, mercury, silver, arsenite, and zinc salts for 48 h at 15°C. Hepatocytes were also exposed to industrial effluent from a metallurgy plant. After the exposure period, hepatocytes were analyzed for metallothionein (MT) and available Zn levels. The results showed that, with divalent metals, available Zn increased with MT levels; there was a significant correlation (R = 0,600; p = 0.0006) between the two. Moreover, the industrial effluent proved to be an inducer of available Zn in hepatocytes, as well as of MT. However, cells exposed to Ag responded with higher levels of available Zn before showing a corresponding MT induction in cells. Inversely, exposure to arsenite led to increased MT without any change in available Zn levels. The value for available Zn tended to be somewhat overestimated in the presence of metals such as Hg, and to a lesser extent Cd. The evaluation of available Zn, in addition to MT, appears to be a valid way of assessing exposure to mono- and divalent metals, though with arsenite, the MT induction response was higher than that of available Zn. The specificity of the available Zn biomarker for heavy metal exposure should be investigated more thoroughly for comparison with the MT biomarker. The measurement of available Zn holds promise as a new biomarker of heavy metal exposure. © 1996 by John Wiley & Sons, Inc.     

Urinary metallothionein and tissue metal levels of rats injected with cadmium, mercury, lead, copper or zinc

Since Cd exposure results in a dose dependent increase in metallothionein level in urine, the present investigation was conducted to examine whether exposure to other divalent cations would also cause an elevation in urinary metallothionein. Female Sprague-Dawley rats were injected subcutaneously with either saline, 5 mumol/kg/day of CdCl2, HgCl2, Pb(C2H3O2)2, CuSO4 or ZnCl2 for 5 days. Significant increases in hepatic Cu levels in rats treated with not only Cu, but also Zn, Cd, or Hg, and in hepatic Zn levels in rats treated with Zn or Cd were noted. Similarly, renal Cu and Zn levels were elevated significantly in all groups except the Pb-injected group. These increases in tissue metal levels were presumably due to induction of metallothionein. The urinary metallothionein level in control rats on day 0, determined by radioimmunoassay, was 0.85 +/- 0.17 mg/g creatinine. There was no significant change in urinary metallothionein level in rats given up to 5 injections of saline or Pb. Hg-injected rats showed 25-fold increase in urinary metallothionein after 5 injections, whereas Cd-injected rats had 9-fold increase. There were also 2- and 3-fold increases of urinary metallothionein by Cu and Zn treatments for 5 days, respectively. Thus, urinary metallothionein levels were elevated in response to Cd, Hg, Cu and Zn, but not Pb; Hg had the most profound effect at equimolar doses.