Arsenic-cadmium interaction in rats

In vitro and in vivo approaches to assess atherosclerosis following exposure to low-dose mixtures of arsenic and cadmium

Worldwide, millions of people are co-exposed to arsenic and cadmium. Environmental exposure to both metals is linked with a higher risk of atherosclerosis. While studies have characterized the pro-atherosclerotic effects of arsenic and cadmium as single agents, little is known about the potential effects of metal mixtures, particularly at low doses. Here, we used a combination of in vitro and in vivo models to assess the effects of low-dose metals individually and as mixtures on early events and plaque development associated with atherosclerosis. In vitro, we investigated early pro-atherogenic changes in macrophages and endothelial cells with metal treatments. The combined cytotoxic effects of both metals at low concentrations were dose interactive, specifically, synergistic in macrophages, but antagonistic in endothelial cells. Despite this differential behavior across cell types, the mixtures did not initiate early pro-atherogenic events: neither reactive oxygen species generation in macrophages nor adhesion molecule expression on endothelial cells. In vivo, we utilized the well-characterized hyperlipidemic apolipoprotein E knock-out (ApoE-/-) mouse model. Previously, we have shown that low concentrations of arsenic (down to 10 ppb) enhance atherosclerosis in ApoE-/- mice. This model has also been used with cadmium to demonstrate pro-atherogenic effects, although at concentrations above human-relevant exposures. In both sexes, there are some small increases in atherosclerotic lesion size, but very few changes in plaque constituents in the ApoE-/- mouse model. Together, these results suggests that low-dose metal mixtures are not significantly more pro-atherogenic than either metal alone.

Toxic Metals and Subclinical Atherosclerosis in Carotid, Femoral, and Coronary Vascular Territories: The Aragon Workers Health Study

OBJECTIVE

Studies evaluating the association of metals with subclinical atherosclerosis are mostly limited to carotid arteries. We assessed individual and joint associations of nonessential metals exposure with subclinical atherosclerosis in 3 vascular territories. Approach and Results: One thousand eight hundred seventy-three Aragon Workers Health Study participants had urinary determinations of inorganic arsenic species, barium, cadmium, chromium, antimony, titanium, uranium, vanadium, and tungsten. Plaque presence in carotid and femoral arteries was determined by ultrasound. Coronary Agatston calcium score ≥1 was determined by computed tomography scan. Median arsenic, barium, cadmium, chromium, antimony, titanium, uranium, vanadium, and tungsten levels were 1.83, 1.98, 0.27, 1.18, 0.05, 9.8, 0.03, 0.66, and 0.23 μg/g creatinine, respectively. The adjusted odds ratio (95% CI) for subclinical atherosclerosis presence in at least one territory was 1.25 (1.03-1.51) for arsenic, 1.67 (1.22-2.29) for cadmium, and 1.26 (1.04-1.52) for titanium. These associations were driven by arsenic and cadmium in carotid, cadmium and titanium in femoral, and titanium in coronary territories and mostly remained after additional adjustment for the other relevant metals. Titanium, cadmium, and antimony also showed positive associations with alternative definitions of increased coronary calcium. Bayesian Kernel Machine Regression analysis simultaneously evaluating metal associations suggested an interaction between arsenic and the joint cadmium-titanium exposure.

CONCLUSIONS

Our results support arsenic and cadmium and identify titanium and potentially antimony as atherosclerosis risk factors. Exposure reduction and mitigation interventions of these metals may decrease cardiovascular risk in individuals without clinical disease.

Influence of co-contaminant exposure on the absorption of arsenic, cadmium and lead

Incidental ingestion of contaminated soil and dust is a major pathway for human exposure to many inorganic contaminants. To date, exposure research has focused on arsenic (As), cadmium (Cd) and lead (Pb), however, these studies have typically assessed metal(loid) bioavailability individually, even when multiple elements are present in the same matrix. As a consequence, it is unclear whether interactions between these elements occur within the gastro-intestinal tract, which may impact absorption and accumulation. In this study, the influence of contaminant co-exposure was assessed using a mouse bioassay and soluble forms of As, Cd and Pb supplied in mouse chow as individual, binary and tertiary elemental combinations. Arsenic urinary excretion and Pb-liver accumulation were unaffected by As-Pb co-exposure (1-10 mg As kg^-1 and 3-30 mg Pb kg^-1) while Cd-kidney accumulation was unaffected by the presence of As and/or Pb. However, Cd co-exposure decreased As urinary excretion and increased Pb-liver accumulation. It was hypothesized that Cd influenced arsenate absorption as a consequence of the impairment of phosphate transporters. Although the reason for increasing Pb-liver accumulation following Cd co-exposure is unclear, enhanced Pb accumulation may occur as a result of transport protein overexpression or changes in divalent metal compartmentalization.

Unknown risk: co-exposure to lead and other heavy metals among children living in small-scale mining communities in Zamfara State, Nigeria

The lead poisoning crisis in Zamfara State, Northern Nigeria has been called the worst such case in modern history and it presents unique challenges for risk assessment and management of co-exposure to multiple heavy metals. More than 400 children have died in Zamfara as a result of ongoing lead intoxication since early in 2010. A review of the common toxic endpoints of the major heavy metals advances analysis of co-exposures and their common pathologies. Environmental contamination in Bagega village, examined by X-ray fluorescence of soils, includes lead, mercury, cadmium, arsenic and manganese. Co-exposure risk is explored by scoring common toxic endpoints and hazard indices to calculate a common pathology hazard risk ranking of Pb > As > Hg >> Cd > Mn. Zamfara presents an extreme picture of both lead and multiple heavy metal mortality and morbidity, but similar situations have become increasingly prevalent worldwide.

Cadmium in blood of Tunisian men and risk of bladder cancer: interactions with arsenic exposure and smoking

Prior investigations identified an association between low-level blood arsenic (As) and bladder cancer risk among Tunisian men but questions remain regarding confounding by cadmium (Cd), a well-established bladder carcinogen. A case-control study of Tunisian men was re-examined to assess the levels of cadmium in blood and reparse the association between the simultaneous exposure to these metals and bladder cancer risk. Levels of blood Cd were significantly twice higher among cases than in controls (P<0.05) and were positively correlated with smoking and age. Additionally, analysis of metal levels among non-smokers according to the region of residence showed very high blood Cd and As levels for the coastal regions of Sfax and central Tunisia. After controlling for potential confounders, for low blood As levels (<0.67 μg/L), the OR for blood Cd was 4.10 (95 % CI 1.64-10.81), while for higher levels (>0.67 μg/L), it was reduced to 2.10 (CI, 1.06-4.17). Adjustment for Cd exposure did not alter the risk associated to As exposure. This study is the first to report the relationship between Cd exposure and risk of bladder cancer occurrence in interaction with smoking and As exposure. Smoking is shown to be the main exposure source to Cd in the Tunisian population but also environmental pollution seems to be responsible of Cd exposure among non-smokers. Exposure assessment studies encompassing a wider population are needed.

Toxicogenomic approaches for understanding molecular mechanisms of heavy metal mutagenicity and carcinogenicity

Heavy metals that are harmful to humans include arsenic, cadmium, chromium, lead, mercury, and nickel. Some metals or their related compounds may even cause cancer. However, the mechanism underlying heavy metal-induced cancer remains unclear. Increasing data show a link between heavy metal exposure and aberrant changes in both genetic and epigenetic factors via non-targeted multiple toxicogenomic technologies of the transcriptome, proteome, metabolome, and epigenome. These modifications due to heavy metal exposure might provide a better understanding of environmental disorders. Such informative changes following heavy metal exposure might also be useful for screening of biomarker-monitored exposure to environmental pollutants and/or predicting the risk of disease. We summarize advances in high-throughput toxicogenomic-based technologies and studies related to exposure to individual heavy metal and/or mixtures and propose the underlying mechanism of action and toxicant signatures. Integrative multi-level expression analysis of the toxicity of heavy metals via system toxicology-based methodologies combined with statistical and computational tools might clarify the biological pathways involved in carcinogenic processes. Although standard in vitro and in vivo endpoint testing of mutagenicity and carcinogenicity are considered a complementary approach linked to disease, we also suggest that further evaluation of prominent biomarkers reflecting effects, responses, and disease susceptibility might be diagnostic. Furthermore, we discuss challenges in toxicogenomic applications for toxicological studies of metal mixtures and epidemiological research. Taken together, this review presents toxicogenomic data that will be useful for improvement of the knowledge of carcinogenesis and the development of better strategies for health risk assessment.

Toxicological assessment of toxic element residues in swine kidney and its role in public health risk assessment

In order to ensure the safety of consumers in Serbia the prevalence of toxic elements (As, Cd, Hg, Pb) in swine kidney collected from three different areas in Serbia (n = 90) was determined by atomic absorption spectrometry. Also, in order to find information on the effects of accumulation of toxic elements on swine kidney, pathohistological examination of the kidneys was performed. The presence of mercury was found in 33.3% of kidney samples in the range of 0.005-0.055 mg/kg, while the presence of cadmium was detected less often (27.7%) but in larger amounts (0.05-1.23 mg/kg). The presence of arsenic was found only in one sample, while no lead was found. The results of the metal-to-metal correlation analysis supported there were the result of different sources of contamination. Pathohistological examination of kidneys confirms tubulopathies with oedema and cell vacuolization. In addition, haemorrhages and necrosis of proximal kidney tubule cells were found. This study demonstrates that toxic elements in Serbian slaughtered pigs are found at levels comparable to those reported in other countries, and consequently the levels reported in this study do not represent a concern from a consumer safety point of view. The lack of a strong correlation between histopathological changes and the incidence of toxic elements found in this study might be explained as the result of synergism among toxic elements and other nephrotoxic compounds which enhance the toxicity of the individual toxins even at the relatively low mean concentrations observed in this study.

Occurrence of ochratoxin A and heavy metals in tissues associated with porcine nephropathy in Serbia

In order to find information on the occurrence of mycotoxic porcine nephropathy in Serbia, during a six month period (2006/2007) samples of blood, kidney and liver from individual animals were collected from healthy slaughtered pigs (n=90) and analysed by HPLC for ochratoxin A (OTA). In addition, the presence of nephrotoxic heavy metals such as cadmium, lead, mercury and arsenic were measured and the kidneys pathohistologically examined. Of the 90 liver samples, 26.6% contained OTA in the range of 0.22-14.5 ng/g. The incidence of OTA in serum and kidney were very similar (30 and 31.1%), but varied between 0.24-220.8 ng/ml and 0.17-52.5 ng/g, respectively. The presence of mercury was confirmed in 33.3% of kidney samples and concentrations ranged between 0.005-0.055 mg/kg, while cadmium was found less frequently (27.7% positive samples) but at higher levels (0.05-1.23 mg/kg). The presence of arsenic was found in only one sample, while lead was not detected in any sample. Histopathological examination of kidneys confirmed tubulopathies with oedema and cell vacuolisation. In addition, haemorrhages and necrosis of proximal kidney tubules' cells were found. These findings indicate that it is likely that most of the kidney injury is related to OTA and other nephrotoxic compounds which enhance the toxicity of OTA.

Roles of biomarkers in evaluating interactions among mixtures of lead, cadmium and arsenic

Human exposure to environmental chemicals is most correctly characterized as exposure to mixtures of these agents. The metals/metalloids, lead (Pb), cadmium (Cd), and arsenic (As), are among the leading toxic agents detected in the environment. Exposure to these elements, particularly at chronic low dose levels, is still a major public health concern. Concurrent exposure to Pb, Cd, or As may produce additive or synergistic interactions or even new effects that are not seen in single component exposures. Evaluating these interactions on a mechanistic basis is essential for risk assessment and management of metal/metalloid mixtures. This paper will review a number of individual studies that addressed interactions of these metals/metalloids in both experimental and human exposure studies with particular emphasis on biomarkers. In general, co-exposure to metal/metalloid mixtures produced more severe effects at both relatively high dose and low dose levels in a biomarker-specific manner. These effects were found to be mediated by dose, duration of exposure and genetic factors. While traditional endpoints, such as morphological changes and biochemical parameters for target organ toxicity, were effective measures for evaluating the toxicity of high dose metal/metalloid mixtures, biomarkers for oxidative stress, altered heme biosynthesis parameters, and stress proteins showed clear responses in evaluating toxicity of low dose metal/metalloid mixtures. Metallothionein, heat shock proteins, and glutathione are involved in regulating interactive effects of metal/metalloid mixtures at low dose levels. These findings suggest that further studies on interactions of these metal/metalloid mixtures utilizing biomarker endpoints are highly warranted.

Metal ions induced heat shock protein response by elevating superoxide anion level in HeLa cells transformed by HSE-SEAP reporter gene

The aim of this work is to define the relationship between heat shock protein (HSP) and reactive oxygen species (ROS) in the cells exposed to different concentrations of metal ions, and to evaluate a new method for tracing the dynamic levels of cellular reactive oxygen species using a HSE-SEAP reporter gene. The expression of heat shock protein was measured using a secreted alkaline phosphatase (SEAP) reporter gene transformed into HeLa cell strain, the levels of superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) were determined by NBT reduction assay and DCFH staining flow cytometry (FCM), respectively. The experimental results demonstrated that the expression of heat shock protein induced by metal ions was linearly related to the cellular superoxide anion level before cytotoxic effects were observed, but not related to the cellular hydrogen peroxide level. The experimental results suggested that metal ions might induce heat shock protein by elevating cellular superoxide anion level, and thus the expression of heat shock protein indicated by the HSE-SEAP reporter gene can be an effective model for monitoring the dynamic level of superoxide anion and early metal-induced oxidative stress/cytotoxicity.

A comparison of 60, 70, and 90 kDa stress protein expression in normal rat NRK-52 and human HK-2 kidney cell lines following in vitro exposure to arsenite and cadmium alone or in combination

Arsenite and cadmium are two potent nephrotoxicants and common Superfund site elements. These elements are included among the stress protein inducers, but information regarding relationships between toxicity produced by combinations of these agents to the stress protein response is lacking. In this study, the immortalized cell lines normal rat kidney NRK-52E and human kidney HK-2 were exposed in vitro to arsenite (As(3+)), cadmium (Cd(2+)), or to equimolar As(3+) plus Cd(2+) mixture combinations for 3 and 5 h over a concentration range of 0.1-100 microM. After a 12-h recovery period, cultured cells were then evaluated for expression of the 60, 70, and 90 kDa major stress protein families. Results indicated that expression of stress proteins varied depending on the species of kidney cells exposed, the exposure concentrations, and the length of exposure to each element on an individual basis and for combined mixtures. For the HK-2 kidney cell line, increased levels of the 70 kDa stress protein was observed for single and combined element exposures whereas there was no change or a decrease of stress proteins 60 and 90 kDa. Increased 70 kDa expression was observed for 10-microM doses of single elements and for a lower dose of 1 microM of the As plus Cd mixture at 3- and 5-h exposures. NRK-52 kidney cells exposed to equivalent doses of As(3+) and Cd(2+) alone or in combination showed increased levels of all stress proteins 60, 70, and 90 kDa. This increase was seen for 10 microM of the As plus Cd mixture at 3 h whereas for single element exposures, increased stress protein levels were generally observed for the 100-microM doses. At 5 h- exposure, 60 and 90 kDa levels increased for 10 microM of Cd(2+) and 60 kDa levels increased for 1 microM of As(3+). However, exposures to 10 microM of the As plus Cd mixture decreased 60 kDa protein expression to control levels at 5 h. For both kidney cell lines, there was a decrease in the stress protein expression levels for all three stress protein families for 100-microM doses of the mixture combination for 3- and 5-h exposures. These data indicate a dose- and combination-related correlation between depression of the stress protein response and the onset of overt cellular toxicity and/or cell death. The threshold for these changes was cell line specific.

Element concentrations in urine of patients suffering from chronic arsenic poisoning

In order to know the element levels in the urine of patients with chronic arsenic poisoning caused by arsenic assimilated from burning coal via air and food, we investigated various elements in the urine of 16 patients with this disease and 16 controls living in the same county in Guizhou Province of China. Concentrations of 25 elements (Al, As, Ba, Be, Bi, Ca, Cd, Cr, Cu, Fe, Ga, Mg, Mn, Mo, Ni, P, Pb, Rb, Sb, Se, Sn, Sr, Ti, V and Zn) were determined by an inductively coupled plasma mass spectrometer or an inductively coupled plasma atomic emission spectrometer. The average concentrations of Cu, Ga and Sn as well as As in the patients were significantly higher, and those of Cr, Rb, Sr and Ti in the patients were significantly lower than the control values. Al, Ba, Mn, Ni and Se were under detection limit in the patients, though they could be detected in the controls. There were no positive correlations between the concentration of As and the concentrations of other elements, including Cu, Ga and Sn in the patients. The results of this study suggest that As from burning coal might influence the urinary excretion of some elements.

Chronic combined exposure to cadmium and arsenic exacerbates nephrotoxicity, particularly in metallothionein-I/II null mice

Cadmium (Cd) and arsenic (As) are important inorganic toxicants in the environment. Humans certainly have the potential to be exposed to the mixtures of Cd and As, but the toxicological interactions of these inorganic mixtures are poorly defined. Metallothionein (MT) is a cysteine-rich, metal-binding protein that plays an important role in Cd detoxication, but its role in As toxicity is less certain. To examine the role of MT in Cd- and/or As-induced nephrotoxicity, MT-I/II-knockout (MT-null) mice and background-matched wild-type (WT) mice were fed CdCl(2) (100 ppm Cd) in the diet, NaAsO(2) (22.5 ppm As) in the drinking water, or Cd plus As for 4 months. Subsequently, nephrotoxicity was examined by morphological and biochemical techniques. Chronic exposure to Cd produced more renal toxicity than As, and the combination of Cd and As produced even more renal injury than caused by either of the chemicals given alone. In mice receiving Cd plus As, proximal tubule degeneration and atrophy, glomerular swelling and interstitial fibrosis were more severe than those produced by either inorganic. Furthermore, lack of MT rendered MT-null mice more sensitive than WT mice to the nephrotoxicity produced by chronic Cd- and/or As-exposure. MT-null mice were especially susceptible to the toxicity produced by the combination of Cd and As, as evidenced by decreased body weight, enzymuria, glucosuria, proteinuria and nephropathy. In conclusion, this study indicates that As may potentiate Cd nephrotoxicity during the long-term, combined exposure, and that intracellular MT plays a role in decreasing the nephropathy of combined exposure to Cd and As.

Effects of lead-arsenic combined exposure on central monoaminergic systems

Lead acetate (116 mg/kg/day), arsenic (11 or 13.8 mg/kg/day as sodium arsenite), a lead-arsenic mixture or vehicle were administered to adult mice through gastric intubation during 14 days. Then, the regional content of norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4 dihydroxyphenyl-acetic acid (DOPAC), 5-hydroxyindole-3-acetic acid (5-HIAA), arsenic, and lead were quantified. Compared with the accumulation after single element exposures, the mixture elicited a higher accumulation of lead and a lower arsenic accumulation in the brain. Compared to controls, lead induced only an augmentation of DOPAC (200%) in the hypothalamus. By contrast, the mixture provoked increases of DOPAC in the hypothalamus (250%), DA and 5-HIAA in the striatum (67 and 187%, respectively) and NE decreased in the hypothalamus (45%). Although these alterations were similar to those produced by arsenic alone, the mixture provoked a 38% decrease of NE in the hippocampus and increases of 5-HT in midbrain and frontal cortex (100 and 90%, respectively) over control values, alterations that were not elicited by either metal alone. These results demonstrate an interaction arsenic/lead on the central monoaminergic systems of the adult mouse.

Sequence of exposure to cadmium and arsenic determines the extent of toxic effects in male Fischer rats

Arsenic and cadmium are both priority hazardous substances and human carcinogens. Although there is the potential for simultaneous exposure to both metals, the interactions of cadmium and arsenic are not well defined. We examined the toxicity of these metals when given alone or in alternating sequence to adult male Fischer rats. In the first study, a non-toxic dose of arsenic (22.5 micromol NaAsO2/kg, s.c.) was given 24 h before cadmium (10, 20, or 30 micromol CdCl2/kg, s.c.) and toxicity was assessed 24 h later. Arsenic pretreatment markedly reduced mortality in rats given the high dose of cadmium (9 survivors/10 treated) compared to rats given cadmium alone (2/10). Arsenic pretreatment also reduced cadmium-induced hepatotoxicity, as indicated by serum glutamic oxalacetic transaminase (SGOT) activity, and markedly reduced cadmium-induced testicular hemorrhagic necrosis. Arsenic pretreatment produced an 8-fold increase in hepatic levels of metallothionein (MT), a metal-binding protein often associated with cadmium tolerance. In the second study, a non-toxic dose of cadmium (3 micromol CdCl2/kg, s.c.) was given 24 h before arsenic (68, 79, 84, or 90 micro/mol NaAsO2/kg. s.c.) and toxicity was assessed 24 h later. Cadmium pretreatment did not alter the lethality of the high dose of arsenic and had no effect on arsenic-induced hepatotoxicity. Although cadmium pretreatment had no effect on arsenic toxicity, it produced large increases in hepatic MT (26-fold) before the arsenic challenge and greatly enhanced MT induction after the challenge. Thus, even though both arsenic and cadmium induce MT synthesis, only arsenic pretreatment protects against cadmium intoxication, and cadmium pretreatment does not effect arsenic toxicity. Thus, toxic interactions of arsenic and cadmium appear to depend on the sequence of exposure.

Enhanced arsenite-induced hepatic morphological and biochemical changes in phenobarbital-pretreated rats

Changes in liver morphology and biochemistry have been assessed 16 hr after a sc injection of sodium arsenite [As(III), 75 mumol/kg] to control and phenobarbital (PB)-pretreated (80 mg/kg, ip daily for 3 days) adult male Wistar rats. As(III) administration to PB-pretreated rats [PB + As(III)] caused hydropic degeneration, total loss of glycogen, necrosis in some centrilobular zones, and an increase in lipid vacuoles around the periportal area. Electron microscopy showed an increased number of vacuoles and autophagosomes containing organelle-like material. There was a 30% decrease in total hepatic cytochrome P-450 (CYP450). O-dealkylation of ethoxy- and pentoxyresorufin and N-demethylation of benzphetamine decreased to 42, 32, and 30% of control values, respectively. 5-Aminolevulinic acid dehydrase decreased 25% from controls, and metal chelatase activities decreased to 25% of the PB-treated group. Injection of As(III) alone resulted in a mild increase in lipid-containing vacuoles around the periportal zone, a moderate loss of glycogen in midzonal areas, and, by electron microscopy, a dilatation of the bile canaliculi and an increase of the number of myelin-like structures. CYP450 content and the O-dealkylation of ethoxy- and pentoxyresorufin and N-demethylation of benzphetamine all decreased between 30 and 50%. These results demonstrate the greater susceptibility of the liver to injury following PB with compounds not requiring metabolic activation. The metabolic basis of these changes are unclear but may result from an increased demand for metabolic energy due to PB induction and decreased adenosine triphosphate synthesis caused by arsenic.

Arsenic increased lipid peroxidation in rat tissues by a mechanism independent of glutathione levels

The role of lipid peroxidation in the mechanism of arsenic toxicity was investigated in female rats pretreated with N-acetylcysteine (NAC, a glutathione [GSH] inducer) or with buthionine sulfoximine (BSO, a GSH depletor). Rats were challenged with sodium arsenite, and sacrificed 1 hr after this treatment. Results showed that arsenic decreased GSH levels and increased lipid peroxidation in liver, kidney, and heart, with a larger effect at 18.2 mg/kg than at 14.8 mg/kg for lipid peroxidation induction. In the liver of rats treated with arsenic, pretreatment with NAC increased the levels of GSH and decreased lipid peroxidation. In kidney and heart, NAC pretreatment protected the tissues against arsenic-induced depletion of GSH levels, but the same degree of protection was not found for lipid peroxidation induction. In its turn, BSO had an additive effect with arsenic in lowering the levels of GSH in the liver and kidney, but an inverse correlation between GSH levels and lipid peroxidation was found only in liver. Arsenic content in tissues of rats pretreated with NAC was lower than in rats treated only with arsenic. In rats with depleted levels of GSH (BSO-pretreated rats), a shift in arsenic tissue distribution was found, with higher levels in skin and lower levels in kidney. A clear tendency for a positive correlation between arsenic concentration and lipid peroxidation levels was found in liver, kidney, and heart.

Testicular lesions by chronic administration of cocaine in rats

Although cocaine is a common drug of abuse, its effects on the testicular structure have not been studied in depth. We report here the testicular lesions produced by chronic cocaine administration to rats. Twenty-eight male Wistar rats weighing 225-250 g were used throughout. Fourteen of them (controls) were injected i.p. with saline solution and the remaining 14 received 30 mg kg-1 day-1 i.p. of aqueous cocaine hydrochloride solution. Animals from both groups were sacrificed at variable times: 7, 15, 30, 45, 60, 75 and 90 days of treatment. Histopathological examination of the testes showed initial alterations at day 15: capillary dilatation; interstitial oedema with lipoid drops due to incipient necrosis of interstitial cells; and necrosis of the cells of the seminiferous tubules. Lesions progressed until 90 days of treatment, showing atrophic and necrotic cells and terminal tubule fibrosis. At this time, the testes were found to be diminished in size. The seminiferous tubules were shrunken, of small diameter and contained necrotic spermatogenic cells and fibrosis. These lesions may produce testosterone diminution and thus sterility due to the disappearance of spermatogenesis.

Toxicological assessment of azarcon, a lead salt used as a folk remedy in Mexico. I. Oral toxicity in rats

Azarcon, a lead tetroxide salt, is used among Mexican and Mexican-American populations for the treatment of digestive illness. Chemical analysis of the azarcon sample used in this study showed it to be 96% lead, 1% calcium, 1% other minor metals, and 2% unidentified material. Taking into account the fact that Pb absorption was estimated at 2% following a single oral administration of 100 mg/kg (Aungst et al., 1981), it is possible to propose a chemical interaction between the components of azarcon, and as a result, the toxicity of Pb tetroxide would be different when given as azarcon than when given as a pure compound. The present work studied this possibility, with the following results. When the treatments of equal doses of pure Pb tetroxide and azarcon were compared (158 mg/kg/day p.o. for 96 h), five of nine tissues studied had similar Pb concentrations. However, with the pure compound the Pb levels were higher in bone and intestines; while with azarcon the Pb levels were higher in heart and brain. The pure Pb tetroxide treatment affects lipid peroxidation only in liver, but a low induction of peroxidation was found also in kidney and heart in rats which received the azarcon treatment. Liver and kidney damage were evident in rats treated with a high dose of azarcon (1.1 g/kg/day p.o. for 96 h), while the effects with the pure compound were similar in type but lower in magnitude. Pb tetroxide as a pure compound inhibits ALA-D by 26% while an inhibition of 42% was found with azarcon.(ABSTRACT TRUNCATED AT 250 WORDS)

Arsenic-cadmium interaction in rats: toxic effects in the heart and tissue metal shifts

Previously, we had shown that arsenic interacts with cadmium in rats; our results showed that the toxicity of a mixture of arsenic + cadmium cannot be predicted by the toxic mechanisms of the individual components. In this paper, we present further evidence about the interaction of arsenic and cadmium in rats. The results were: arsenic modified the 24 h-LD50 value of cadmium more clearly than cadmium did with the one of arsenic; based on the LD50 values, the mixtures we studied were more toxic than either metal alone. With single doses (As 10 mg/kg, Cd 2.6 mg/kg, and As 10 mg/kg + Cd 2.6 mg/kg) the mixture As + Cd was more toxic than each metal. At these doses, cadmium significantly induces the levels of glutathione, metallothionein, and lipid peroxidation in heart tissue, as compared to a saline group of rats. Arsenic incremented glutathione and lipid peroxidation at higher values than those obtained with cadmium. The mixture of As + Cd behaved as arsenic in the induction of lipid peroxidation and glutathione and like cadmium in metallothionein induction. Finally, rats treated with As + Cd had less Cd in liver than animals treated only with cadmium, and more As in heart tissue than rats treated only with arsenic. Our results give further evidence about the arsenic-cadmium interaction in rats, demonstrate the utility of employing different biomarkers in the study of chemical mixtures and indicate that heart tissue is affected not only by the mixture of As + Cd, but also by either metal alone.