Lead–cadmium interaction effect on the responsiveness of rat mesenteric vessels to norepinephrine and angiotensin II

Dose-Dependent Differential Effects of In Vivo Exposure of Cadmium on Myometrial Activity in Rats: Involvement of VDCC and Ca2+-Mimicking Pathways

Present study was undertaken to study the effect of 28-days exposure of female adult rats to cadmium (Cd) in drinking water @ 3, 10 and 30 parts per million (ppm) on myometrial responsiveness to different spasmogens and unravel the possible mechanism of alterations in myometrial activity. Cadmium and Ca²⁺ levels in blood and uterus were measured by atomic absorption spectroscopy while isometric tension in myometrial strips was measured using data acquisition system-based physiograph. Dose-dependent increase in levels of cadmium was observed in both blood and uterus while calcium was increased only in the uterus as compared to those in control. Significant increase in absolute tension and mean integral tension along with non-significant increase in frequency of myometrial contraction was observed in rats of Cd-treated groups. As compared to the control, cadmium decreased and increased the effects of calcium chloride, 80 mM KCl, histamine (0.1 μM) and oxytocin (10^-2 IU/ml) in lower-dose (3 ppm) and higher-dose groups (10 and 30 ppm), respectively. Cadmium potentiated and inhibited the relaxant response to phenylephrine in myometrium of rats at lower-dose (3 ppm) and highest-dose (30 ppm) Cd-treated groups, respectively. Results of our study revealed that Cd accumulates in the myometrium of rats and alters its responsiveness to oxytocin, histamine, 80 mM KCl, calcium chloride and phenylephrine, and these effects are differentially mediated depending on levels of exposure possibly through voltage-dependent calcium channel (VDCC) and Ca²⁺-mimicking pathways.

Combined toxicity and underlying mechanisms of a mixture of eight heavy metals

With the rapid development of modernization and industrialization in China, a large quantity of heavy metals, including zinc, copper, lead, cadmium and mercury, have been entering the atmosphere, soil and water, the latter being the primary route of pollution. In the present study, in vitro experiments were performed to examine the joint toxicity and the underlying mechanisms of the eight most common heavy metals contaminating offshore waters on the eastern coast of Ningbo region. Using a cell cycle assay, cell apoptosis and reactive oxygen species (ROS) detection methods, the present study demonstrated that the heavy metal mixture arrested JB6 cells at the S phase, induced the generation of ROS and cell apoptosis. A luciferase assay indicated that the levels of activator protein‑1 and nuclear factor‑κB transcription factors were upregulated. Upregulation of the protein levels of C‑jun and p65 were detected in the JB6 cells by western blot analysis; these two genes have important roles in cell carcinogenesis. These results provide a useful reference for further investigations on the combined toxicity of the exposure to multiple heavy metals.

Functional involvement of L-type calcium channels and cyclic nucleotide-dependent pathways in cadmium-induced myometrial relaxation in rats

Modulation of myometrial spontaneity by cadmium (Cd) and its regulatory pathways was studied in rat uterus in the absence and presence of blockers of different signaling pathways. Isometric tension in myometrial strips, under a resting tension of 1 g, mounted in organ bath containing Ringer-Locke solution (RLS) continuously aerated with carbogen, was measured using data acquisition system-based physiograph and Lab Chart Pro V7.3.7 software. Mean integral tension was measured for 8 min. Cd (1 nM-0.1 mM) not only produced concentration-dependent inhibitory effect on rat myometrium but it (10 µM) also significantly ( p < 0.05) inhibited calcium chloride and BAY K-8644-induced myometrial contraction. Glybenclamide (10 µM), 4-aminopyridine (1 mM), and propranolol (10 µM) failed to significantly attenuate Cd-induced inhibitory responses, while L-NAME (0.1 mM), 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 25 µM), and 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ 22536; 1 µM) significantly ( p < 0.05) produced inhibitory effects on Cd-induced myometrial relaxation. Phenylephrine (1 nM-10 µM) and salbutamol (0.01 nM-0.1 µM)-induced relaxant effects on rat myometrium were significantly potentiated by 10 µM Cd. Thus based on the results of present functional study, it may be inferred that inhibitory effects of Cd on rat myometrium are mediated through blockade of L-type calcium channels and activation of NOS-NO-sGC and/or AC-cAMP pathways.

The impact of subchronic cadmium poisoning on the vascular effect of nitric oxide in rats

The aim of this study was to evaluate the impact of poisoning with cadmium in hypertensive doses (50 or 200 ppm in drinking water for three months) on the basal and stimulated release NO effect in the isolated and perfused rat mesenteric bed. Mesenteric artery preparation preconstricted by norepinephrine (0.5 μg/mL) was used to determine changes in its vascular resistance induced by e-NOS synthase blocker, N-ω-nitro-L-arginine (L-NOARG) injected in increasing doses from 1.0 to 200.0 μg or acetylcholine (ACh) administered in doses from 0.05 × 10-10 to 5.0 × 10-10 mol before and during L-NOARG infusion (1.0 μg/mL). Vascular reactivity was measured as an increase or decrease in perfusion pressure in the constant flow system.

Rats poisoned with 50 or 200 ppm of cadmium demonstrated a significant decrease (P < 0.05) in vascular response to L-NOARG used in doses of 50 or 100 μg. The dose-response curve obtained for L-NOARG was shifted to the right and ED50 value was greater in the group of rats given cadmium in a dose of 200 ppm than in the controls (70.39 ± 10.7 versus 25.79 ± 4.8 μg, P < 0.01). These rats reacted with lower expressed vasodilatation to ACh in doses to 0.2 ± 10-10 mol. In all poisoned rats, L-NOARG enhanced the effect of ACh used in doses from 0.05 to 0.5 ± 10-10 mol, whereas in the control group this effect was only achieved at 0.1 ± 10-10 mol. The serum nitric oxide concentration was decreased (P B < 0.05) in both groups of cadmium-treated rats. These results suggest that cadmium in hypertensive doses modifies the vascular effect of NO in basal conditions and after stimulation by ACh.

A new fluorescent chemosensor for Pb²⁺ ions based on naphthalene derivatives

A new naphthalene derivative receptor (L) was synthesized and characterized with common spectroscopic methods. L exhibited a strong fluorescence enhancement in the presence of trace amounts of Pb(2+), attributable to photoinduced electron transfer (PET) effect, which also displayed high selectivity over a series of other metal cations (Na(+), K(+), Cs(+), Mg(2+), Ba(2+), Cr(3+), Mn(2+), Fe(3+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) in acetonitrile/H2O (9:1, v/v) mixture.

Heart function in magnetic resonance imaging and the mesenteric artery reactivity in rats receiving lead-contaminated drinking water

The aim of this study was to evaluate the effect of lead (Pb)-contaminated drinking water on magnetic resonance imaging (MRI)-estimated cardiac function, vascular reactivity, and serum lipids in rats. For 3 months, male Wistar rats, aged 4–6 weeks, were given drinking water with the addition of lead acetate at a concentration of 100 ppm Pb (10 rats) or water free from Pb (8 control rats). The cardiac MRI was performed at rest and under β-adrenergic stimulation on a 4.7 T scanner using electrocardiogram-triggered gradient echo (FLASH) cine sequence. After 1–2 weeks of the MRI test, experiments were performed ex vivo. After stabilization of perfusion pressure (PP), norepinephrine at doses from 0.01 to 5.0 μg was dissolved in Krebs solution, injected in a volume of 100 μl, and next infused at a concentration of 0.5 μg/ml into the isolated mesenteric artery. In this manner, preconstricted mesenteric bed was used to determine PP changes induced by acetylcholine, given at doses from 0.05 to 5.0 μg, before and during the infusion of nitric oxide synthase inhibitor (1.0 μg/ml). At the end, dobutamine (5 mg), followed by potassium chloride (10.5 mg), was injected. Lipid levels were determined enzymatically, blood Pb level was measured by the atomic absorption spectrophotometer. This study showed that Pb impairs the left ventricular systolic and diastolic function. Pb-induced changes in response to resistance of vessels to vasoactive agents may be secondary to the reduced left ventricular ejection fraction. The high-density lipoprotein subfraction 2 (HDL2) is involved in the cardiovascular effect of Pb.

Effects of cadmiumin vitro on contractile and relaxant responses of isolated rat aortas

OBJECTIVE

Cadmium is known to affect the vascular tone of isolated blood vesselsin vitro and the arterial pressure of ratsin vivo. However, the mechanisms of cadmium actions on the vascular system have not been clarified. To elucidate the actions of cadmium on vascular tonus, effects of cadmium on vasocontractile and vasorelaxant responsesin vitro were investigated using aortic strips isolated from rats.

METHODS

Aortic strips isolated from male Wistar rats were incubated with CdCl(2) (10μM) for 24 hr, washed with fresh CdCl(2)-free medium, and then used for measurement of isometric tension and Western blot analysis of eNOS (endothelial nitric oxide synthase) and iNOS (inducible nitric oxide synthase).

RESULTS

In the aortas pretreated with cadmiumin vitro, the contractile response to phenylephrine was significantly higher than that in the control aortic strips pretreated with a vehicle. The sodium nitroprusside-induced relaxing response was significantly higher in the aortic strips pretreated with cadmium for 24 hr, compared with that in the control pretreated with a vehicle. The isoproterenol-induced relaxing response was also significantly higher in the cadmium-accumulated aortic strips.In vitro cadmium treatment slightly but not significantly increased the acetylcholine-induced relaxation of the aortic strips. Cadmium treatment induced expression of iNOS and significantly increased expression of eNOS in the aortic strips, while it did not affect expression of β-actin.

CONCLUSIONS

Cadmium treatmentin vitro augmented the α1 adrenoceptor-mediated contractile response, even though eNOS and iNOS were upregulated by cadmium treatment. NO-induced and β-adrenoceptor-mediated relaxing responses were also augmented by cadmium treatment. These results suggest that both vasocontractile and vasorelaxing responses are augmented in cadmium-accumulated aortas.

Environmental and occupational exposure to lead as a potential risk factor for cardiovascular disease

We have evaluated current knowledge on relations between environmental and occupational exposure to lead with a strong emphasis on cardiovascular disease risk factors, such as the influence of lead compounds on lipid disturbances and arterial blood pressure. In addition, "novel" biochemical and vascular risk factors for cardiovascular diseases were discussed, as well as the combination of lead exposure and genetic predisposition to cardiovascular diseases. Occupationally and educationally, awareness of the unfavourable effects of lead on cardiovascular diseases risk factors should be emphasised. Indeed, accurate identification of the various mechanisms that might account for the effects of lead on the cardiovascular system should be of the highest priority in this field of research.

Involvement of the epidermal growth factor receptor in Pb²+-induced activation of cPLA₂/COX-2 genes and PGE₂ production in vascular smooth muscle cells

Lead (Pb²+) is one of the most common heavy metal pollutants, which can cause chronic cardiovascular diseases. To clarify the mechanism by which Pb²+ induces inflammatory reactions, we examined the expression of inflammatory genes including encoding cyclooxygenase-2 (COX-2), cytosolic phospholipase A₂ (cPLA₂), and their down stream product prostaglandin E₂ (PGE₂) in CRL1999 cells that is a vascular smooth muscle cell line from human aorta. The expression of COX-2/cPLA₂ genes and PGE₂ secretion was increased markedly after cells were exposed to 1 μM Pb²+. PD098059, a MEK inhibitor, suppressed Pb²+-mediated inflammatory reactions; this indicates the involvement of the phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). Furthermore, Pb²+-induced activation of the COX-2/cPLA₂ genes was inhibited by both epidermal growth factor receptor (EGFR) inhibitors (AG1478 and PD153035) and EGFR siRNA. Short-term stimulation with Pb²+ induced EGFR phosphorylation at the Tyr residue (position, 1173). Importantly, overexpression of EGFR resulted in a significant potentiation effect on Pb²+-induced gene expression. Taken together, our results indicate that 1 μM Pb²+ can induce PGE₂ secretion by upregulating the transcription of COX-2/cPLA₂ genes. EGFR is the key target in the plasma membrane responsible for transmitting Pb²+ signals in order to trigger downstream inflammatory cascades.

Lead exposure effect on angiotensin II renal vasoconstriction

Low levels of chronic lead exposure can produce hypertension and endothelial dysfunction, which could be associated with oxidative stress, changes in vascular tone and an imbalance of endothelial-derived vasoconstriction and vasodilator factors. The aim was to investigate the effect of chronic lead-exposure on angiotensin II-induced vasoconstriction in isolated perfused kidney and microvessels. Male Wistar rats (230-250 g) were treated for 12 weeks with lead acetate (100 ppm, Pbgroup) or pure water (control group). We evaluated the vascular reactivity in the kidneys and renal microvessels in the presence and absence of N(omega)-nitro-L-arginine methyl ester (L-NAME) in both groups. The nitrite concentration in renal perfusate was measured as an index of NO released, renal abundance of 3-nitrotyrosine was measured as well as endothelial NO synthase (eNOS) expression. Oxidative stress was measured by using the oxidative fluorescence dye dihydroethidium (DHE) to evaluate in situ production of superoxide and identified by confocal microscopy. Lead-exposure significantly increased blood pressure, eNOS protein expression, oxidative stress and vascular reactivity to angiotensin II. L-NAME potentiated vascular response to angiotensin II in control group but had no effect on the Pb-group. Nitrites released from the kidney of lead-group was lower compared to the control group while 3-nitrotyrosine was higher. This data suggest that lead-induced hypertension could be caused partially by an altered NOsystem.

Direct effects of lead (Pb2+) on the relaxation of in vitro cultured rat aorta to acetylcholine

Lead (Pb(2+)) exposure is related to increased blood pressure or hypertension of human or animals. Abnormal vascular relaxant responses of low level Pb(2+) exposed animals were reported by several studies. However, it is difficult to tell whether these effects were induced directly by Pb(2+) or not. In this study we hypothesized that Pb(2+) can directly affect the relaxation of vessels. Male Wistar rat aortae were removed and cultured in PMRI 1640 with 1 ppm Pb(2+) (4.8 microM lead acetate) for 0.5, 6, 12 and 24h, and then their responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were examined. After incubated for 24h, the relaxation induced by ACh was significantly decreased in Pb(2+) exposed aortic rings. However, there was not significant difference in relaxation induced by SNP between Pb(2+) exposed and control group. The nitrite in the culture media of aortic rings cultured for 24h, measured with Griess method, was significantly decreased in the Pb(2+) exposed group. The expression of endothelial NOS (eNOS) and isoform NOS (iNOS) in the homogenate of aortic rings cultured for 24h was measured by Western blot. The expression of eNOS of the Pb(2+) exposed group was significantly upregulated compared with that of the control group. However, there was no significant difference in the expression of iNOS in control and Pb(2+) exposed group. In conclusion, Pb(2+) was able to directly affect the relaxation of rat aorta. This effect may have some relation with the lower level of NO in the media, though the expression of eNOS was upregulated.

Oxidative damage in liver after perinatal intoxication with lead and/or cadmium

Lead acetate (300 mg Pb/L) and/or cadmium acetate (10mg Cd/L) in blood and liver were administrated as drinking water to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21), to investigate the toxic effects in blood and in the liver. Both metals produced mycrocitic anaemia in the pups as well as oxidative damage in the liver, as suggested by the significant increase in TBARS production and the high catalase activity. Moreover, intense alkaline and acid phosphatase activity, used as biomarkers of liver adaptation to damaging factors, was observed. In addition, the toxikinetics are different for Pb and Cd: while Cd is a hepatotoxic from day 0, Pb is not until day 21. Finally, simultaneous perinatal administration of both metals seems to protect, at least, in the liver TBARS production against the toxicity produced by Cd or Pb separately.

Lead and other trace metals in preeclampsia: a case-control study in Tehran, Iran

To assess the effects of environmental exposures to trace metals on the incidence of preeclampsia, concentrations of lead (Pb), antimony (Sb), manganese (Mn), mercury, cadmium, cobalt and zinc in umbilical cord blood (UCB) and mother whole blood (MWB) were measured in 396 postpartum women without occupational exposure to metals in Tehran, Iran, using inductively coupled plasma mass spectrometry. Mother's ages ranged from 15 to 49 (mean 27) years. Preeclampsia was diagnosed in 31 subjects (7.8%). Levels of Pb, Sb and Mn in UCB were significantly higher in preeclampsia cases [mean+/-SD of 4.30+/-2.49 microg/dl, 4.16+/-2.73 and 46.87+/-15.03 microg/l, respectively] than in controls [3.52+/-2.09 microg/dl, 3.17+/-2.68 and 40.32+/-15.19 microg/l, respectively] (P<0.05). The logistic regression analysis revealed that one unit increase in the common logarithms of UCB concentration of Pb, Sb or Mn led to increase in the risk of preeclampsia several-fold; unit risks (95% CI) were 12.96 (1.57-107.03), 6.11 (1.11-33.53) and 34.2 (1.81-648.04) for Pb, Sb and Mn, respectively (P<0.05). These findings suggest that environmental exposure to Pb, Sb and Mn may increase the risk of preeclampsia in women without occupational exposure; levels of metals in UCB to be sensitive indicators of female reproductive toxicity as compared with those in mother MWB. Further studies are necessary to confirm these findings, especially on Sb and Mn.

Influence of lead (Pb2+) on the reactions of in vitro cultured rat aorta to 5-hydroxytryptamine

Although several studies demonstrated that lead induced abnormal vascular responses in low level lead exposed animals, investigations of the direct effects of lead on blood vessels are limited. In this study we tested the hypothesis that lead was able to directly affect the contractile reactivities of vessels. Male Wistar rat aortae were removed and cultured in PMRI 1640 with 1 ppm lead acetate for 0.5, 6, 12, 24 and 48 h, and then their responses to norepinephrine bitartrate (NE) and serotonin (5-hydroxytryptamine, 5-HT) were examined. The contractile responses to 5-HT of lead exposed aortae were significantly increased when the aortae were cultured for 24 and 48 h. Denudation of endothelium was able to abolish the increased contractile response completely. Diphenyleneiodonium (DPI), an inhibitor of the NAD(P)H oxidase, could abolish the increased contractile response to 5-HT. However, Vitamin C (VC) enhanced the contractile response of both groups to higher dosages of 5-HT. The expression of 5-HT(2B) receptor was not significantly altered by incubation with 1 ppm lead for 24 h. These data suggest that exposure to low levels of lead can directly increase the contraction of aorta to 5-HT. This effect is endothelium dependent, which is not mediated by increased expression of the 5-HT 2B receptor. The increased contraction to 5-HT may be related to increased production of superoxide (O2*-) induced by lead exposure.

The impact of subchronic lead poisoning on the vascular effect of nitric oxide in rats

Lead-induced arterial hypertension is suggested to have resulted mainly from a reduction in nitric oxide (NO) bioactivity in vessel walls. The aim of this study was to evaluate the impact of poisoning by lead in so-called hypertensive doses on the basal and stimulated released NO effect in the rat mesenteric bed. Male Buffalo rats were given lead in a dose of 50 or 100ppm in drinking water for three months. The isolated mesenteric bed preconstricted by norepinephrine (0.5μg/ml) was used to determine the changes in vascular resistance induced by N-ω-nitro-l-arginine injected in increasing doses from 1.0 to 200.0μg or by acetylcholine administered in doses from 0.05 × 10(-10) to 5.0 × 10(-10)mol. These changes were measured as an increase or decrease in perfusion pressure in the constant flow system. In comparison with controls rats given 50ppm of lead, an increase in maximal response to N-ω-nitro-l-arginine (P < 0.01) and acetylcholine (P < 0.05) and a shift to the left of the dose-response curve for acetylcholine were demonstrated. Vascular responses in rats, who were given 100ppm of lead, were similar to those observed in the control group. It is concluded that lead induces NO-mediated changes of vascular tone and vascular reactivity only in the small range of doses known as hypertensive.

Involvement of cholinoceptors in cadmium-induced endothelial dysfunction

Cadmium (Cd) toxicity was produced in male rats to study the role of cholinoceptors in Cd-induced endothelial dysfunction. The changes in the tension of the aortic rings to constrictor and dilator agonists were compared with those of controls. A Cd-induced significant increase in phenylephrine response was associated with a decrease in basal dilator prostanoid release. In Cd-exposed rings, despite an obvious depression in the acetylcholine (ACh) response, the receptor-independent dilation to the calcium ionophore A23187, which elicits a receptor-independent endothelial relaxation, was slightly elevated (p<0.01), but the smooth muscle cell response to the NO donor, sodium nitroprusside (SNP) remained unaltered. Cadmium decreased both the maximal response to ACh (10(-5) M) and its pirenzepine (Prz) sensitive component. The M1 type cholinoceptor-mediated response to ACh decreased in Cd-exposed rings to 10.30 +/- 5.00% from 38.40 +/- 6.90% (p<0.001). Cadmium also reduced the share of indomethacin 1.64% to 13.92 +/- 2.89% (p<0.01), which correlated well with the changes in the M1-mediated response (r=0.991, p<0.0001). Most of the deleterious effect of Cd appears to be restricted to the M1-dependent ACh response. These findings suggest that Cd produces an endothelial dysfunction by impairing the M1 type cholinoceptor mediated response, which seems to be involved in prostanoid release.

Study of the activity of several brain enzymes like markers of the neurotoxicity induced by perinatal exposure to lead and/or cadmium

Five enzymes, considered keys to the correct function of the central nervous system (CNS) were chosen to study their utility as markers of the possible neurotoxic effects produced by the perinatal exposure to lead and/or cadmium. With this aim, lead acetate (300 mg/l) and/or cadmium acetate (10 mg/l) were administered to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21). Brains were used to determine the activity of acid phosphatase (ACP), alkaline phosphatase (ALP), catalase (CAT), acetylcholinesterase (AchE) and ATP-ases (Na(+)/K(+) and Mg(2+)/Ca(2+) dependent). The general decrease of the activity of these enzymes observed after the treatment with heavy metals suggests that lead and cadmium are able to reach the CNS and impair its function by neurochemical changes. On the other hand, the results showed an increase of the activity of CAT; which possibly indicates that lead and cadmium might have other mechanisms of action, such as increasing oxidative damage in the CNS. Finally, the study of the effects produced by the simultaneous administration of lead and cadmium suggests that, in general, both metals exert an additive effect, either competing for the same inhibitory binding sites or increasing cellular damage. In conclusion, the study of the activity of enzymes is revealed as an effective method to measure the neurotoxicity induced by lead and cadmium.

Biomarkers of renal effects in children and adults with low environmental exposure to heavy metals

The health effects of chronic exposure to heavy metals such as lead, cadmium, and mercury are widely documented, yet few data exist about the renal impact of low environmental exposure to these metals, particularly in children. The aim of this study was to assess renal parameters in children and adults living in an environment known for its past heavy metal contamination around two nonferrous smelters in northern France (Noyelles-Godault and Auby) and to compare their results with age and gender-matched controls living in neighboring municipalities with unpolluted soil (total: 400 children, 600 adults, sex ratio = 1). The integrity of renal function was assessed by measuring the urinary excretion levels of total protein, albumin, transferrin, beta(2)-microglobulin, retinol-binding protein, brush border antigen, and the enzyme N-acetyl-beta-D-glucosaminidase (NAG). The mean blood concentrations of lead (Pb-B, children </=42.2 micro/L, adults </=71.3. micro/L) and of cadmium (Cd-B, children </=0.52 microg/L, adults 0.86 microg/L) were all relatively low, indicating a low uptake of these heavy metals from the environment despite relatively high levels in soil (between 100 and 1700 ppm for lead and 0.7 to 233 ppm for cadmium). Pb-B levels were, however, significantly increased in boys, girls, and women--but not men--living in the polluted area. Boys, men, and women living in the polluted area had also on average higher Cd-B levels. The concentrations of mercury in urine (Hg-U) were by contrast similar in control and exposed groups. None of the renal parameters studied showed a significant difference between control and exposed groups. The influence of heavy metals on renal parameters was further assessed by stepwise multiple regression, testing Pb-B, Cd-B, Hg-U, age, gender, body mass index (BMI), urinary creatinine levels, and area of residence as predictors in both children and adults, including first-order metal interaction terms, smoking habits, and alcohol consumption in adults. The only positive correlation was found between the urinary excretion of NAG activity (standardized for BMI and urinary creatinine) and Cd-B levels when taking the whole children population, indicating that even low cadmium burdens may produce subtle effects on the proximal tubule in children, although deleterious consequences are unlikely should exposure not increase. However, in the absence of other positive findings even after studying the smaller subgroups with higher levels of heavy metals, these results are clearly indicative of the minimal renal impact of living around nonferrous smelters that are currently complying with pollution regulations, even when soil contamination is still high.