Oncogenicity of rat prostate cells transformed in vitro with cadmium chloride

Three rat ventral prostate (RVP) cell lines transformed after in vitro treatment with cadmium chloride (CdCl₂) and one control untreated cell line were tested for tumorigenicity in newborn rats. All three cadmium-transformed RVP cell lines induced tumors at the site of inoculation in 95–100% of animals. The fibroblastoid RVP56Cd cell line induced sarcomas, whereas the epithelial cell lines RVP47-3G and RVP47-3F produced highly differentiated squamous cell carcinomas. About 20% of animals injected with RVP47-3G developed lung and splenic metastases. The tumors could be further passaged into young rats. The sarcomas had a hyperdiploid modal chromosome number similar to that of the RVP56Cd cell line. Carcinomas induced by the RVP47-3G cell line had a large proportion of stromal metaphases. The modal chromosome number of these carcinomas was in the hypertriploid-hypotetraploid range, similar to that of the parental cell line. These results demonstrate that treatment of RVP cells with CdCl₂ in vitro results in neoplastic transformation. Since both fibroblastoid and epithelial prostate cells have undergone transformation, it seems possible that cadmium acted as a carcinogen without cell specificity. The susceptibility of these cells to the carcinogenic effect may be related to their resistance to cadmium. In the process of neoplastic transformation induced by CdCl₂ in RVP epithelial cells changes of squamous metaplasia occur, and probably precede acquisition of tumorigenicity.This work was supported in part by an American Cancer Society Institutional Grant     

Effects of cadmium on proliferation and self-renewal activity of prostate stem/progenitor cells

Cadmium (Cd) is an occupational and environmental pollutant that induces numerous pathological effects, including injuries to prostate. The aim of the present study was to investigate the effects of Cd on self-renewal and proliferation of prostate stem/progenitor cells (PSPC) and its possible mechanisms. Prostate epithelial cells were prepared from mice to form sphere in Matrigel/PrEGM supplemented with cadmium chloride (CdCl₂). The data showed that CdCl₂ inhibits sphere-forming ability and proliferation of PSPC in a concentration dependent manner. Primary spheres were then passaged to form daughter spheres and we found that CdCl₂ suppressed PSPC self-renewal activity, which recovered after further passaging. We also detected the protein level of androgen receptor (AR) in the spheres of each passage. The results showed that AR in primary spheres is suppressed by CdCl₂ in a concentration dependent manner. However, no obvious change of AR was found in subsequent passages. The in vivo toxicity of CdCl₂ on PSPC was detected by giving mice drinking water with CdCl₂. Our results demonstrated in vivo inhibition effect of CdCl₂ on self-renewal activity of PSPC. Consistent with in vitro results, self-renewal activity of PSPC was recovered after CdCl₂ withdrawal. In addition, CdCl₂ also in vivo suppressed PSPC proliferation as indicated by Ki67 immunostaining. Our finding suggested that Cd may inhibit proliferation and self-renewal activity of PSPC by suppressing AR, which could be important to further understanding the complex mechanism of Cd toxicity in prostate.     

Differential induction of MAP kinase signalling pathways by cadmium in primary cultures of mouse embryo limb bud cells

While it is well accepted that mammalian embryos may develop abnormally in response to harmful environmental stresses, the molecular changes that embryonic cells undergo are not always clear. In the present study we examined the induction of mitogen-activated protein kinase (MAPK) pathways by cadmium chloride (CdCl₂) in micromass cultures of limb bud cells from day 11 BALB/c mouse embryos. CdCl₂ exposure was found to cause a marked reduction in both cell survival and differentiation in these cultures. To study stress signalling pathways, cells were lysed and were examined for the phosphorylation of three MAPKs. It was shown that 4 μM CdCl₂ treatment of limb bud cells caused the phosphorylation of c-Jun N-terminal kinase (JNK), but not p38 or extracellular signal-regulated kinase (ERK), over a 120 min period. The results indicate a specific activation of the JNK pathway in response to CdCl₂-induced toxicity in mouse limb bud cells.     

The synthesis of metallothionein and cellular adaptation to metal toxicity in primary rat kidney epithelial cell cultures

Single cells were isolated from rat (100–150 g) kidney cortex slices by mild trypsinization. They were plated on plastic culture dishes and were maintained in a selective Eagle's D-Valine Minimum Essential Media (MEM) to form an epithelial cell monolayer culture. The fibroblast growth was retarded by D-Valine. The cells in monolayer culture accumulated cadmium when they were incubated with a ¹⁰⁹CdCl₂ (10^?5 M) containing medium. The synthesis of metallothionein by these cells was demonstrated by incorporation of [³⁵S]cysteine and ¹⁰⁹CdCl₂ into a heat stable protein (mol. wt 10 000) within 8 h of exposure and also by immunoprecipitation using a specific antibody to rat liver metallothionein. The cytotoxic effects of Zn²⁺, Cu²⁺, Cd²⁺ and Hg²⁺ were studied in culture after addition of various concentrations of metal salts (10^?5 –10^?2 M). Disrupted cellular colonies with severe cell damage were observed after addition of 10^?3 M Cd²⁺ or Hg²⁺ as CdCl₂ or HgCl₂ while similar toxicity was observed only after addition of 10^?2 M Zn²⁺ or Cu²⁺ as ZnSO₄ or CuSO₄ to confluent cell cultures. The cellular damage due to Cd²⁺ was protected when the cells were pretreated with Cd²⁺ (10^?5 M) for 24 h and these cells could tolerate much higher concentrations of cadmium (10^?2 M). These results indicate a direct protective role of intracellular metallothionein in the cellular toxicity of cadmium.     

Mitigative action of monoisoamyl-2,3-dimercaptosuccinate (MiADMS) against cadmium-induced damage in cultured rat normal liver cells

Cadmium is non-essential, carcinogenic and multitarget pollutant in the environment. Monoisoamyl-2,3-dimercaptosuccinate (MiADMS) is an ester of dimercaptosuccinic acid that acts as an antioxidant and chelator. Therefore, the mitigative action of MiADMS on viability, morphology, antioxidative enzymes and cell cycle were studied on rat liver cells treated with cadmium chloride (CdCl₂). The cells were treated with 150 μM CdCl₂ alone or cotreated with 300 μM MiADMS (concurrently, 2 h or 4 h post-CdCl₂ treatment) for 24 h. The viability of cells treated with CdCl₂ alone was decreased in comparison to the control cells. Cotreatment with MiADMS resulted in an increase in cell viability in comparison to the CdCl₂ alone treated cells. The CdCl₂ treatment altered the morphological shape of the cells, while cotreatment with MiADMS restored the shape. Antioxidative enzymes activities were decreased in the cells treated with CdCl₂ alone, while MiADMS cotreatment resulted in an increase in enzyme activities. The CdCl₂ arrested the cells in S phase of the cell cycle. Cotreatment with MiADMS alleviated cell cycle arrest by shifting to G1 phase. These results clearly show the mitigative action of MiADMS on CdCl₂ toxicity and may suggest that MiADMS can be used as an antidote against cadmium.     

Comparison of the sensitivity of different toxicological endpoints in Caco-2 cells after cadmium chloride treatment

The human colorectal adenocarcinoma cell line Caco-2 is a widely used in vitro model of the intestinal barrier. Cadmium chloride (CdCl₂) is a highly toxic metal compound, ubiquitous in the biosphere, able to enter the food chain and to reach the intestinal epithelium, causing structural and functional damages. The aim of this work was to characterise cadmium toxicity in Caco-2 cells and, in particular, to compare the sensitivity of different endpoints revealing damage both on the epithelial barrier and at the cellular or molecular level. After 24-h exposure of the cells to CdCl₂, lactate dehydrogenase (LDH) leakage showed cadmium-induced cell toxicity, significant from 25 µM CdCl₂ and above, and analysis of different cell death pathways indicated the presence of necrosis after treatment with 50 µM CdCl₂. At the molecular level, we observed an increase in the protective protein heat shock protein 70 (HSP70), starting at 10 µM CdCl₂. At the barrier level, transepithelial electrical resistance (TEER) decreased while paracellular permeability (PCP) significantly increased after the treatment, showing an EC₅₀ of 6 and 16 µM CdCl₂, respectively, and indicating the loss of barrier integrity. In conclusion, our data reveal that CdCl₂ toxicity in Caco-2 cells can be detected at the barrier level at very low concentrations; also, HSP70 was shown to be a sensitive marker for detecting in vitro cadmium-induced toxicity.     

Effect of cadmium (CdCl2) on cell proliferation and production of EDRF (endothelium-derived relaxing factor) by cultured human umbilical arterial endothelial cells

The effect of cadmium chloride (CdCl₂) on cell proliferation and EDRF (endothelium-derived relaxing factor) production by cultured human umbilical arterial endothelial cells (HUAECs) was investigated. The viability of HUAECs decreased dose-dependently after the addition of Cd (cadmium chloride). Morphologic examination by phase contrast microscopy revealed severe damaging effects of Cd at higher concentrations. The cytotoxic effect of Cd on DNA synthesis was also concentration-dependent. The effect of Cd on EDRF production by indomethacin-treated HUAECs was assessed by its anti-platelet aggregatory effect. Platelet aggregation studies were carried out in cuvettes lined with HUAECs using an aggregometer. The anti-platelet aggregatory effect was decreased dose-dependently by pretreatment with Cd. These findings suggest that HUAECs are susceptible to concentration-dependent Cd cytotoxicity, and that Cd can inhibit the production of EDRF by HUAECs. Received: 14 February 1994 / Accepted: 3 May 1994     

Factors influencing cadmium uptake and cytotoxicity in cultured cells

1. Cultured Chinese hamster B14F28 and HeLa cells in early lag and stationary phases accumulated less cadmium than cells in logarithmic growth.

2. Pretreatment of the cell cultures with a non-toxic concentration of cadmium lead to adaptation of the response to subsequent high concentrations. The pretreated cells did not differ from controls in their uptake of cadmium.

3. HeLa cell cultures accumulated more cadmium than B14F28 cultures and differed in their sensitivity to cadmium. The cytotoxicity of cadmium in the two cell lines did not correlate with uptake of cadmium.

4. Cells accumulated more cadmium and exhibited enhanced toxicity with increasing pH of the medium. Serum and serum albumin reduced the uptake of cadmium and the cytotoxicity. Increasing concentrations of calcium ions depressed the uptake of cadmium, while magnesium and phosphate ions exerted no effect.     

Attenuation of cadmium chloride induced cytotoxicity in murine hepatocytes by a protein isolated from the leaves of the herb <Emphasis Type="Italic">Cajanus indicus</Emphasis> L.

Cadmium has been recognized as a strong environmental pollutant. Exposure to this heavy metal occurs through the intake of foodstuffs, drinking water and also via the inhalation of air. Present study was conducted to evaluate the protective effect of a 43 kDa protein, isolated from the leaves of the herb Cajanus indicus, against cadmium-induced cytotoxicity in hepatocytes. For this study, cadmium chloride (CdCl₂) has been used as the source of cadmium. Treatment of hepatocytes with 800 μM CdCl₂ for 3 h caused significant reduction in cell viability in association with the increased levels of glutamate pyruvate transaminase (GPT) and alkaline phosphatase (ALP) leakage. The activities of the antioxidant enzymes, superoxide dismutase, catalase (CAT), glutathione-S-transferase and glutathione reductase, and the levels of cellular metabolites, reduced glutathione (GSH) as well as total thiols have also been decreased under the same treatment. In addition, the toxin enhanced the levels of the lipid peroxidation end products and oxidized glutathione (GSSG). Incubation of hepatocytes with the protein at a dose of 0.1 mg/ml for 3 h prior to the toxin treatment (at a dose of 800 μM for 3 h) restored the activities of all the antioxidant enzymes, the levels of GSH, total thiols, cell viability and also attenuated the increased levels of GPT, ALP, lipid peroxidation and GSSG. In addition, the protein resisted CdCl₂ induced alterations of all the parameters when applied in combination with CdCl₂. Effects of a known antioxidant, vitamin E, and a non-relevant protein, bovine serum albumin against CdCl₂ induced cytotoxicity have also been included in the study. Combining all, we would like to say that the protein possessed protective activity against CdCl₂ induced cytotoxicity in mouse hepatocytes probably via its antioxidant property. Mahua Sinha and Prasenjit Manna contributed equally in the study.     

Prevention of cadmium-induced toxicity in liver-derived cells by the combination preparation Hepeel(®)

Cadmium is a heavy metal of considerable environmental concern that causes liver damage. This study examined the possible prevention of cadmium toxicity in human HepG2 cells and primary rat hepatocytes by Hepeel^®, a combined preparation of tinctures from seven different plants. Hepeel^® prevented cadmium chloride (CdCl₂)-induced cell death in both HepG2 cells and hepatocytes, and also reduced the loss of glutathione, lipid peroxidation, nuclear fragmentation, caspase activation and release of mitochondrial cytochrome C. To compare their relative efficacy, the seven constituent plant tinctures of Hepeel^® were also separately tested. The tinctures China and Nux moschata, which exert solely anti-oxidative effects, failed to reduce cytotoxicity, and only protected against loss of glutathione and lipid peroxidation. In contrast, the tinctures Carduus marianus and Chelidonium, demonstrated anti-apoptotic effects, and protected HepG2 cells and primary hepatocytes against CdCl₂-induced cell death. These results demonstrate how the effectiveness of Hepeel^® is determined by the synergistic features of its constituent tinctures. Furthermore, we conclude that cadmium toxicity in the liver is mainly due to stimulation of the intrinsic apoptotic pathway, but may be intensified by increased oxidative stress.     

Impairments of bone marrow hematopoietic cells followed by the sever erythrocyte damage and necrotic liver as the outcome of chronic in vivo exposure to cadmium: novel insights from quails

Cadmium is a heavy metal classified as an environmental hazard, and its toxicity is subject to extensive research. Japanese quails were exposed to cadmium chloride (CdCl₂) ad libitum for 20 days. Bone marrow, peripheral blood and liver were analyzed following the exposure. Moreover, we have provided the very first explanation of hematopoietic lines in Japanese quail. Following CdCl₂ exposure, changes in the number, size and morphology of blood cells were observed in both peripheral blood and bone marrow. Alterations included severe erythrocyte damage, monocytosis and lymphopenia. In the liver of Cd-exposed animals we observed necrotic cells, absence of hematopoietic regions and cytogenetic changes of hepatocytes. Alterations in the bone marrow were also noted, as well as giant phagocytic cells, most likely macrophages. In vivo, CdCl₂ exposure caused swift and destructive changes in the hematopoietic niche, liver and other tissues responsible for the detoxification cycle of cadmium and its compounds.     

Modulation of cytokines and chemokines expression by NAC in cadmium chloride treated human lung cells

Cadmium (Cd), is one of the most hazardous metals found in the environment. Cd exposure through inhalation has been linked to various diseases in lungs. It was shown that Cd induces proinflammatory cytokines through oxidative stress mechanism. In this report, we studied the immunomodulatory effect of a well known antioxidant, N‐acetylcysteine (NAC) on cadmium chloride (CdCl₂) treated human lung A549 cells through human cytokine array 6. The lung cells were treated with 0 or 75 µM CdCl₂ alone, 2.5 mM NAC alone, or co‐treated with 2.5 mM NAC and 75 µM CdCl₂ for 24 h. The viability of cells was measured by crystal violet dye. The array results were validated by human IL‐1alpha enzyme‐ linked immunosorbent assay (ELISA) kit. The viability of the 75 µM CdCl₂ alone treated cells was decreased to 44.5%, while the viability of the co‐treated cells with 2.5 mM NAC was increased to 84.1% in comparison with untreated cells. In the cell lysate of CdCl₂ alone treated cells, 19 and 8 cytokines were up and down‐regulated, while in the medium 15 and 3 cytokines were up and downregulated in comparison with the untreated cells. In the co‐treated cells, all these cytokines expression was modulated by the NAC treatment. The IL‐1α ELISA result showed the same pattern of cytokine expression as the cytokine array. This study clearly showed the modulatory effect of NAC on cytokines and chemokines expression in CdCl_2‐treated cells and suggests the use of NAC as protective agent against cadmium toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1612–1619, 2016.     

Cytoprotective and antigenotoxic potential of Mangiferin,a glucosylxanthone against cadmium chloride induced toxicity in HepG2 cells

Mangiferin (MGN), a glucosylxanthone present in large amounts in the leaves and edible mango fruits of Mangifera indica. Here, we report about MGN’s potential for mitigating cadmium chloride (CdCl₂) induced cytotoxic and genotoxic effects in HepG2 cells growing in vitro. The cytoprotective potential was assessed by MTT, clonogenic and apoptotic assays, while antigenotoxic effect by micronucleus and comet assay. The established cytotoxic and genotoxic effects were well indicated after CdCl₂ treatment and was mitigated by pretreatment with MGN. MGN prior to CdCl₂ treatment increased the cell survival (MTT), surviving fraction (clonogenic assay) and inhibited sub-G₁ population (flow cytometric analysis). Further, inhibition of CdCl₂ induced apoptotic cell death by MGN was confirmed by microscopic and DNA fragmentation assays. A significant (p < 0.01) reduction in the micronuclei frequency and comet parameters after MGN pretreatment to CdCl₂ clearly indicated the antigenotoxic potential. Similarly, the reactive oxygen species generated by the CdCl₂ treatment were inhibited significantly (p < 0.001) by MGN. Taken together, our study revealed that MGN has potent cytoprotective and antigenotoxic effect against CdCl₂ induced toxicity in HepG2 cell line and which may be attributed to decrease in CdCl₂ induced reactive oxygen species levels and resultant oxidative stress.     

Molecular mechanisms involved in the adaptive response to cadmium-induced apoptosis in human myelomonocytic lymphoma U937 cells

We examined the molecular mechanisms involved in the adaptive response to cadmium (Cd)-induced apoptosis in human myelomonocytic lymphoma U937 cells. When U937 cells were treated with 50 μM cadmium chloride (CdCl₂) for 12 h, significant apoptosis occurred. This was associated with an increase in intracellular reactive oxygen species (ROS), sustained phosphorylation of JNK, activation of caspase-3, a decrease in Mcl-1 (anti-apoptotic Bcl-2 proteins), and increases in Bim, Noxa and tBid (a pro-apoptotic protein under the Bcl-2 family). No apoptosis occurred when the cells were treated with 1 μM CdCl₂ for 72 h. However, pretreatment with low-dose CdCl₂ dramatically altered the sensitivity of the cells to 50 μM CdCl₂ with inhibition of apoptosis. Concomitantly, there were significant decreases in the generation of intracellular ROS and the activation of JNK. Pretreatment with 1 μM CdCl₂ also attenuated the decrease in Mcl-1 and the increases in Bim, Noxa and tBid induced by 50 μM CdCl₂. In conclusion, pretreatment with low-dose Cd inhibited apoptosis induced by high-dose Cd. The mechanism involves inhibition of intracellular ROS generation and JNK activation, and modulating the balance between the expression of Mcl-1 and its binding partners, Bim, Noxa and tBid.     

Design and synthesis of 2‐phenyl benzimidazole derivatives as VEGFR‐2 inhibitors with anti‐breast cancer activity

Three new series of 2‐phenyl benzimidazole‐based derivatives were designed, synthesized, and evaluated for their in vitro cytotoxic activity against breast cancer (MCF‐7) cell lines. Three compounds 8 , 9 , and 15 showed high cytotoxic activities, with IC₅₀ values of 3.37, 6.30, and 5.84 μM, respectively, while they showed comparable cytotoxicity to the standard drug doxorubicin against human normal cells, including nontumorigenic breast epithelial cell line (MCF‐10F), skin fibroblast cell line (BJ), and lung fibroblast cell line (MRC‐5). Six of the synthesized compounds were screened against vascular endothelial growth factor receptor 2 (VEGFR‐2) where compounds 8 , 9 , 12 , and 15 exhibited an outstanding potency in comparison with sorafenib, with IC₅₀ values of 6.7–8.9 nM. Molecular docking study assessed the good binding patterns of the most potent compounds with the reported conserved amino acids of VEGFR‐2 active site.     

Design,synthesis, and docking study of new quinoline derivatives as antitumor agents

New quinolines substituted with various heterocycles and chalcone moieties were synthesized and evaluated as antitumor agents. All the synthesized compounds were in vitro screened against 60 human cancer cell lines. Compound 13 showed the highest cytotoxicity toward 58 cell lines, exhibiting distinct growth inhibition values (GI₅₀) against the majority of them, including SR, HL‐60 (TB) strains (leukemia), and MDA‐MB‐435 strains (melanoma), with GI₅₀ values of 0.232, 0.260, and 0.300 µM, respectively. It exhibited great selectivity toward cancer cell lines, with less toxic effect against normal cells represented by skin fibroblast (BJ) and breast epithelial cell lines (MCF‐10F). The enzyme inhibitory activity of compound 13 was evaluated against topoisomerase 1 (Topo 1), epidermal growth factor receptor and vascular endothelial growth factor receptor 2, where it displayed worthy Topo 1 inhibition activity with an IC₅₀ value of 0.278 µM compared with camptothecin as a reference drug (IC₅₀ 0.224 µM). Docking studies were performed to investigate the recognition profile of compound 13 with the Topo 1 enzyme binding site.     

Neuron and glial cell marker proteins as indicators of heavy metal-induced neurotoxicity in neuroblastoma and glioma cell lines

The sensitive and specific biochemical indicators for assessing chemical-induced neurotoxic insults in cell culture models have not been sufficiently explored. This study was designed to assess the usefulness of glia-specific beta-S100 protein and neuron-specific enolase (NSE) as indices of in vitro neurotoxicity of heavy metals. Glioma C₆ and neuroblastoma N18TG-2 cells were grown in Dulbecco's modified Eagle's medium containing various concentrations of mercuric chloride (HgCl₂) or cadmium chloride (CdCl₂) for 5 days. Toxic response patterns of the neurospecific endpoints (beta-S100 and NSE), which were monitored with enzyme immunoassays, were compared with those of the non-neurospecific endpoints such as cell viability, total cellular protein, lactate dehydrogenase (LDH) activity, and cumulative glucose consumption in the two cell lines. Both HgCl₂ and CdCl₂ produced dose-dependent inhibition of neurospecific endpoints and non-specific endpoints. However, by ranking the EC₅₀ values (effective concentration producing half-maximal inhibition) for various endpoints, the lowest values were found for beta-S100 in C₆ cells, and for NSE in N18TG-2 cells. In lower and intermediate concentrations, the inhibitory effects of the heavy metals on the content of beta-S100 and NSE occurred in the absence of any detectable effect on intracellular LDH activity, and independently of total cellular protein inhibition. The sensitive and excess responses of the neurospecific endpoints relative to that of the non-specific endpoints may reflect the specific neurotoxic insults of the heavy metals on the cultured cells. The highly sensitive and nerve cell-specific changes of the two marker proteins after in vitro treatments with HgCl₂ and CdCl₂ indicate their usefulness as indicators of in vitro assessment of neurotoxicity.     

CHRONIC TOXIC AND CARCINOGENIC EFFECTS OF ORAL CADMIUM IN THE NOBLE (NBL/Cr) RAT: INDUCTION OF NEOPLASTIC AND PROLIFERATIVE LESIONS OF THE ADRENAL,KIDNEY, PROSTATE,AND TESTES

Based on the occurrence of pulmonary cancers in exposed populations, cadmium is classified as a human carcinogen. More controversial target sites for cadmium in hum ans include the prostate and kidney, where some studies have shown a link between cadmium and cancer. In Wistar rats cadmium induces tumors in the ventral prostate. The relevance of such lesions to humans is debated since the rat ventral lobe, unlike the dorsolateral lobe, has no embryological homolog in the human prostate. Cadmium has not been linked with renal tumors in rodents but is a potent nephrotoxin. In this work we studied the effects of oral cadmium in the Noble (NBL/Cr) rat with particular attention to proliferative lesions of the prostate and kidneys. Cadmium (as CdCl₂) was given ad libitum throughout the study in the drinking water at doses of 0, 25, 50, 100, and 200 ppm Cd to groups (initial n = 30) of male rats, which were observed for up to 102 wk. At the lower doses of cadmium ( 50 ppm) a clear dose-related increase in total proliferative lesions of the prostate (ventral and dorsolateral lesions combined) occurred (0 ppm = 21% incidence, 25 ppm = 46% , 50 ppm = 50% ; trend p &lt; .03). These lesions were described as intraepithelial hyperplasia with occasional areas of atypical epithelial cells without stromal invasion. The lesions occurred primarily in the dorsolateral prostate with cadmium exposure and most frequently showed three or more foci within each specimen. At higher doses, prostatic proliferative lesions declined to control levels. The loss of prostatic response at the higher doses was likely due to diminished testicular function secondary to cadmium treatment. This was reflected in lesions indicative of testicular hypofunction at the highest cadmium dose, namely, interstitial cell hyperplasia, and a strong correlation between cadmium dose and total proliferative lesions of the testes (hyperplasias and tumors combined). Renal tumors (mainly mesenchymal and pelvic transitional cell), although few in number, showed a positive correlation with cadmium dose, as did pelvic transitional epithelial hyperplasia. Renal lesions were not associated with any cadmium-induced changes in age-related chronic nephropathy. The incidence of pheochromocytomas of the adrenal was increased by cadmium but only at the 50 ppm dose. Inflammatory lesions of the liver and spleen were common at higher doses and showed strong trends based on dose. These results indicate that oral cadmium can induce proliferative lesions in the prostate and kidney of the Noble rat. The finding of proliferative lesions of dorsolateral prostate in rats has presumed relevance to human prostate cancers.     

Cadmium-metallothionein-induced nephropathy

Cadmium-metallothionein (Cd-Mt) was isolated from livers of rats repeatedly injected with small doses of cadmium (0.6 mg Cd/kg). Intraperitoneal injection of isolated Cd-Mt to control rats (1.2 mg Cd/kg) resulted in accumulation of a large percentage of the injected cadmium in the kidney (about 60 to 70%), whereas most Cd from the ip injection of a similar dose of CdCl₂ was recovered from the liver. The intracellular partitioning of Cd, whether given as Cd-Mt or CdCl₂, was similar. Cd given as CdCl₂ was bound to large molecular weight proteins isolated from cytoplasm 4 hr after Cd injections; Cd given as Cd-Mt was isolated as Cd-Mt. Changes in the morphology of renal tubular cells are observed both by light and electron microscopy in these rats within 4 hr after Cd-Mt injection. Necrosis of proximal renal tubular lining cells was observed within 24 hr. No ultrastructural changes were found in renal tubular cells after CdCl₂ injection. These studies demonstrate that the circulating Cd-Mt complex was nephrotoxic. It may also have a major role in the pathogenesis of Cd-induced renal disease following long-term exposure to cadmium.