Electron Microscopic Study of Cadmium Nephrotoxicity in the Rat

Morphological characterisation of BGM (Buffalo Green Monkey) cell line exposed to low doses of cadmium chloride

Morphological changes in the Buffalo Green Monkey (BGM) cell line after exposure to a subcytotoxic dose (0.062 mM, equivalent to EC(10)-effective concentration 10%) of cadmium chloride have been evaluated. Cells were exposed for 24 h and the effects observed at the ultrastructural level by transmission and scanning microscopy. Using transmission electron microscopy, the most notable findings in treated cells were the presence of intranuclear inclusion bodies and thin intracytoplasmic granules associated to myelin figures and the presence of apoptotic bodies. Other morphological alterations included cell vacuolisation and a reduced cytoplasm volume, condensation of the mitochondria and a decreased number of cytoplasmic organelles, except lysosomes and autophagic vacuoles, which increased in number. Scanning electron microscopy pointed to a cell with a disrupted perinuclear region and a decrease in the number of surface microvilli. We conclude that the BGM cell line may be considered an useful tool for toxicological studies involving cadmium.

The integrity of renal cortical brush-border and basolateral membrane vesicles is damaged in vitro by nephrotoxic heavy metals

Poisoning of experimental animals with cadmium (Cd), mercury (Hg), lead (Pb) or cis-diamminedichloroplatinum (cis-Pt) causes shortening and focal loss of microvilli in proximal tubule (PT) cells, thus indicating that the reduced reabsorptive surface due to damaged integrity of brush-border membrane (BBM) may contribute to the reabsorptive and secretory defects in these toxic states. In addition, in in vitro studies with isolated renal cortical BBM vesicles (BBMV), heavy metals (HM) inhibit transport of various compounds, and these data were interpreted as being a result of a direct inhibition of the respective membrane transporters. In this work we used a DeltapH-driven acridine orange fluorescence quench assay to test if various divalent cations affect in vitro the integrity of BBMV and basolateral membrane vesicles (BLMV) isolated from the rat renal cortex. In Cd-treated BBMV we found that: (a) the integrity of vesicles decreased with increasing concentrations of Cd; and (b) the loss of sealed vesicles was high at 37 degrees C, intermediate at 25 degrees C, and very low at 0 degrees C. The loss of sealed BBMV was caused also by Hg, Cu, Pb and Zn (Hg>>>Cu=Cd>Pb=Zn). Cis-Pt, Al, Fe, Ba, Mg and Mn had no effect. BLMV were damaged by HM with an efficiency Hg>>>Cd=Pb=Cu, whereas other divalent cations, including Zn, were ineffective. An SH-group protector, dithiothreitol, prevented the loss of sealed vesicles in some (Hg, Pb, Cu) but not in all (Cd, Zn) cases. We conclude that the nephrotoxic HM directly damage the integrity of PT cell plasma membranes; this may cause shortening and loss of microvilli and basolateral invaginations in HM-treated experimental animals in vivo. The data also indicate that caution should be taken when effects of HM on various transports are studied in isolated membrane vesicles in vitro; an impaired transport may result from the loss of vesicle integrity, and not necessarily from the direct inhibition of a transporter.

Cytotoxicity, zinc protection, and stress protein induction in rat proximal tubule cells exposed to cadmium chloride in primary cell culture

Primary cell culture was utilized to study the relationships between stress protein induction by zinc in vivo and cadmium toxicity in vitro. Effects of cadmium on cell viability were evaluated by the alamar blue assay, in conjunction with the ultrastructural morphology of cells by transmission electron microscopy. The expression of stress protein gene products was evaluated by 35S two-dimensional gel electrophoresis. The results showed cytotoxicity of CdCl2 at and above 129 microM (14.55 micrograms cadmium/mL medium) following 4 h of exposure. Prior zinc administration (20 mg zinc/kg, s.c., two daily doses) in vivo significantly protected the cells in vitro as demonstrated by improved cell viability. The 35S labeling of proteins induced by CdCl2 exposure clearly demonstrated for the first time that gene product of the 70-kDa family was induced in cultured rat proximal tubule cells which are the target cells for cadmium toxicity in vivo. Zinc in vivo pretreatment of animals induced proteins in the 90-, 70-, and 38-kDa families, which may act together with metallothionein to protect cells against cadmium toxicity. The results also indicate that the protective effect of zinc remains after the cells have been put in culture and thus provides a system in which we can study the changes that occur as a result of zinc exposure that decreases cadmium toxicity.

Morphological effects of cadmium on proximal tubular cells in rats

Twenty-four male rats of the Wistar strain divided into four groups were injected s.c. with a dose of 0.8, 1.5, and 3.0 mg Cd/kg body wt as CdCl2 in saline, and saline alone to the control rats, three times a week for 3 wk. Cadmium levels of whole kidney homogenate, supernatant (cytosol), precipitate, and metallothionein (MT) fraction were measured. Histological changes of the renal proximal tubules were investigated by optical and electron microscopy. In the kidneys, Cd levels were increased with the increment of Cd dosage; 80-90% of Cd was contained in cytosol, and 55-75% was in MT fraction. Non-MT-Cd reached a maximum in the 1.5 mg Cd group, whereas that of the 3.0 mg Cd group showed some decline. With increasing Cd doses, the size of nuclei and nucleoli in the cells of proximal tubule showed significant enlargement and also an increase in the number of nucleoli on light microscopy. At higher doses, chromatin condensation of the tubular nuclei and vacuolar degeneration of the tubular cells were evident. On electron microscopy, perichromatin granules of the proximal tubular nuclei were increased in number, especially in the rats of Cd 0.8 mg and 1.5 mg/kg groups. As the Cd doses increased, ring-shaped nucleoli were increased in number and nucleolar segregation was observed more clearly. Moreover, in the 3.0 mg/kg Cd group, nuclear indentation and nucleoli containing compact dense granules were observed. In the cytoplasm, there was an increase of lysosomes, myelin bodies, ring-shaped mitochondria, and vesiculation; ultimate changes were degeneration and cell necrosis. The injured cells were heterogenously distributed in each nephron and this heterogeneity was attributed in the difference in Cd content and cell cycle in each cell of the nephron.

Pathological study on beagles after long-term oral administration of cadmium

Histopathological, histochemical, and electron microscopic examinations were performed on beagles after a long-term oral cadmium (Cd) administration of greater than 8 years. Although renal atrophy was remarkable in groups receiving doses of 50 and 100 mg/kg body weight/day, bone lesions could not be demonstrated by roentgenological and histopathologic examination. It was noticed that concomitant regeneration or recovery and cell death of the epithelium occurred in the proximal convoluted tubules. The cell death was consistent with apoptosis, a special feature of cell death, which was shown to play a major part in the tubular damage of cadmium by electron microscopic examination. Fatty degeneration of the pars recta tubules was seen to show dose-dependence. The intrarenal cadmium was localized predominantly in the cytoplasm of the proximal tubular epithelium by histochemical and ultracentrifugal cell fractionation examinations. Although no remarkable changes were found in the other organs, aggregates of siderophages in the liver and focal hemorrhage in the spleen, known as spontaneous lesions, might be related to Cd intoxication. In conclusion, the present study revealed that no bone lesions occur with Cd administration in adult beagles in spite of long-term administration. An excessive cell death to regeneration or recovery in the proximal tubules might result in the renal cortical atrophy. No remarkable changes were seen in the glomeruli and distal nephrons, which were in good agreement with Cd distribution.

Correlation of cadmium-induced nephropathy and the metabolism of endogenous copper and zinc in rats

Female Wistar rats were injected (sc) every second day for 8 weeks with Cd (0.25 mg/kg) as CdCl2. After only a 2-week exposure, when cadmium (Cd) concentration in liver was about 13 micrograms/g, ultrastructural examinations revealed some irregular ergastoplasm systems and significant proliferation of smooth endoplasmic reticulum in the hepatocyte ultrastructure. The increase in Zn content occurred simultaneously with the increase in Cd concentration in the liver (Zn to Cd ratio was 1:1). In the kidneys after a 3-week exposure, when Cd concentration was 7 micrograms/g, the concentration of endogenous Cu increased. At the same time the urinary excretion of that metal was considerably higher than that of the control group. In the kidneys after a 4-week exposure, when Cd concentration in this organ exceeded 10 micrograms/g tissue, injured brush border microvilli and swollen mitochondria in the proximal convoluted tubular cells were seen. In renal corpuscules, fusion between the podocyte pedicles was also found. The changes in renal cortex ultrastructure became more pronounced when Cd concentration in kidney was increasing. Necrotic changes in the examined organ were observed when Cd concentration increased to about 30 micrograms/g tissue. The critical concentration in renal cortex of about 200 micrograms/g tissue should be revised. The present margin of safety with regard to risk of renal effects is small.

Non-metallothionein-bound cadmium in the pathogenesis of cadmium nephrotoxicity in the rat

Male rats were injected SC with 0.6 mg Cd/kg/day for 5 days per week for 2, 4, 6, and 8 weeks. Liver and kidney were examined morphologically and analyzed for metallothionein, cadmium, zinc, and copper. Morphologic changes were found in kidney but not in liver. The earliest ultrastructural change consisted of myelin figures in vacuoles in cytoplasm of proximal tubular lining cells reflecting degeneration of membranes. This change occurred after 4 weeks with 801 +/- 25 nmol/g (89.9 micrograms/g) total kidney cadmium or 390 nmol/g (43.7 micrograms/g) of cadmium not bound to metallothionein. Similar changes were observed after 6 weeks but after 8 weeks pathological changes consisted of focal cellular necrosis and interstitial fibrosis. Other ultrastructural changes included altered mitochondria and increased numbers of microbodies. Renal cadmium after 8 weeks exposure was 1827 +/- 48 nmol/g (215.3 +/- 5.8 micrograms/g) or 628 nmol/g (70.2 micrograms/g) of cadmium not bound to metallothionein. Total cadmium was higher in liver than in kidney but partitioning between bound and nonbound cadmium differed in the two organs. The fraction not bound to metallothionein increased with time of exposure in both liver and kidney. However, total cadmium in the liver did not exceed potentially available binding sites of metallothionein, whereas total cadmium did exceed potentially available binding sites of metallothionein in the kidney where pathologic changes occurred. The results indicated that degeneration of cellular membranes is an early cellular effect of cadmium exposure followed later by toxicity to organelles, cellular necrosis, and interstitial fibrosis. Cadmium-induced cellular toxicity is more directly related to the fraction of cadmium in the kidney that is not bound to metallothionein than is total cadmium per se.

An electrophysiological freeze fracture assessment of cadmium nephrotoxicity in vitro

Human proximal tubule cell cultures exposed to doses of cadmium chloride (CdCl2) between 0.05 microgram/ml and 0.5 microgram/ml exhibited alterations in cell membrane structure and transport function. At these Cd concentrations, cell numbers were not significantly altered from control values in either nonreplicating confluent, or actively replicating subconfluent cultures. Transmission electron microscopy revealed few alterations in cultures treated with 0.05 microgram/ml Cd. Tight junctions were intact; organelles and myeloid body formation appeared normal. Freeze fracture analysis confirmed the integrity of the tight junctions as well as increased numbers of vesicles or pits along the lateral cell membrane, indicating increased endocytotic activity. Cells exposed to 0.1 microgram/ml Cd were characterized by decreased numbers of microvilli and inhibited myeloid body formation. Cd doses of 0.5 micrograms/ml elicited nuclear chromatin condensation, fragmented sealing strands in 5 to 10% of the tight junction profiles, sparse microvilli, and inhibited myeloid body formation. Electrophysiologic assessments of transport function by Ussing chamber analysis revealed decreases in transepithelial potentials for all three concentrations, with significant differences at Cd concentrations of 0.5 to 0.1 micrograms/ml. Cells treated with 0.5 micrograms/ml Cd also exhibited slight decreases in electrical resistance, consistent with the minimal fragmentation of sealing strands observed in freeze fracture replicas. Resistance in cultures treated with 0.1 or 0.05 micrograms/ml Cd remained within control values and indicated that drops in potential difference and short circuit current in these cells reflected true alterations in ion transport.

Identification of groups at risk for renal diseases (including nephrotoxicity)

An assessment of the health significance of renal disease due to nephrotoxicity and identification of groups at risk for toxic nephropathy is difficult because the incidence is likely to be underestimated in the available registry data. In more than 50% of all cases of end-stage renal failure, the causality is not known. In end-stage toxic nephropathy, the kidney may show the morphological changes of chronic interstitial nephritis as well as those of chronic glomerulonephritis. Therefore, additional epidemiological data and information on exposure are necessary. Physiological, social and educational factors may aggravate exposure, and the role of multiple exposures is unknown, although individuals at risk are not only those with the highest burden of exposure. Differential sensitivity is explained in part by genetic factors, as shown for abnormal sulphoxidation and slow acetylation. Early identification of groups at risk for nephropathy of clinical significance still relies on the methods of classical nephrology, i.e., measurement of proteinuria or decreased glomerular filtration rate, but several new tests are currently under evaluation.

Impaired urine concentrating ability in Itai-itai (ouch-ouch) disease

A case of Itai-itai (ouch-ouch) disease with reduced urinary kallikrein excretion and slightly enhanced renin-angiotensin-aldosterone system is described. Although it is well known that cadmium toxicity frequently affects the renal tubular lesions, this report is the first to demonstrate the impaired urine concentrating ability in this disease.

Cadmium, NAG activity, and beta 2-microglobulin in the urine of cadmium pigment workers

Cadmium (Cd), N-acetyl-beta-D-glucosaminidase (NAG) activity, beta 2-microglobulin (BMG), and creatinine (cr) in urine were measured during April and September 1986 in workers exposed to cadmium pigment dust (maximum exposure 3.0 micrograms/m3/8 h for respirable dust). In April and September urinary Cd ranged from 0.2 to 9.5 and from 0.5 to 7.0 micrograms/g cr with a geometric mean of 0.7 and 1.2 micrograms/g cr, respectively. The correlation coefficient between Cd and NAG was 0.261 (n = 61) in April and 0.389 (n = 50) in September. The correlation coefficient between Cd and BMG was 0.241 (n = 63) in April and 0.115 (n = 50) in September. It appears that urinary Cd concentrations have a closer relation with urinary NAG than urinary BMG, even when urinary Cd concentrations are less than 10 micrograms/g cr. It is concluded that NAG is a more sensitive indicator of Cd absorption than BMG even at urinary Cd concentrations of less than 10 micrograms/g cr.

Female reproduction and pup survival and growth for mice fed a cadmium-containing purified diet through six consecutive rounds of gestation and lactation

Female CF1 mice were bred for 6 consecutive, 42-d rounds of gestation-lactation. Their purified diets contained cadmium added at either 0.25, 5.0, or 50.0 ppm Cd; at each cadmium level, the diets were either sufficient or deficient in certain vitamins, minerals, and fat. The deficient diet at 5 ppm cadmium was designed to simulate conditions implicated in the etiology of itai-itai disease among multiparous women in Japan. Fertility, litter size, pup survival, and pup growth (weaning weight) are reported for mice on the six diets during each of the six rounds of gestation/lactation. Except for fertility, decreases in reproductive measures that occurred in response to dietary deficiencies or cadmium during round 1 of reproduction were repeated, unchanged in magnitude, in each successive round. For sufficient diet groups, 50 ppm cadmium had no effect on fertility or pup survival during lactation, but caused a 15% decrease in litter size at birth and a 25% decrease in pup growth. Dietary deficiencies alone decreased all four measures of reproductive performance: fertility by 12%, litter size by 30%, pup survival by 18%, and pup growth by 42%. In addition, dietary deficiencies strikingly decreased the incidence of consecutive pregnancies. Combined effects of 50 ppm cadmium and dietary deficiencies were additive for all reproductive measures except fertility; for fertility, cadmium caused no decrease in the fertility of sufficient-diet animals, but caused a striking 45% decrease in deficient-diet animals. Relating our results to humans, women who contracted itai-itai disease (analogous to mice on the deficient, 5 ppm cadmium diet), in addition to their characteristic bone disease, could have experienced decreases in fertility and in growth of their offspring related to their dietary deficiencies. In addition, their diet-related decreases in fertility could have been enhanced by their combined exposure to cadmium.

Cadmium-induced changes in avian renal morphology

The effects of i.m. administered cadmium on growth rate and nephromorphology were studied in young pullets. The growth rate of pullets treated with 0.6 mg Cd2+/kg at 48-h intervals was severely retarded, reaching only 50% of normal growth by 21 days. Such a decrease in growth rate was prevented when cadmium was given with either ferric or magnesium EDTA chelate. Electron micrographs of kidney tissue from cadmium intoxicated birds revealed massive intracellular disorganisation of proximal tubular cells, showing increased vacuolation and dilated endoplasmic reticulum. Mitochondria were few and swollen with reduced cristae. Some disorganisation was noted in the group treated with MgEDTA in conjunction with cadmium, with normal morphology observed in the group treated with FeEDTA plus cadmium. In general, glomerular morphology of intoxicated pullets appeared normal, except that a 25% increase in thickness of the glomerular basement membrane was evident. No such membrane thickening was observed in any of the chelate treated groups. These findings indicate that both chelates can provide certain levels of protection, in terms of growth rate and morphology, from cadmium intoxication. The possible mechanisms by which chelates offer protection have been discussed, but many questions remain unanswered.

Cadmium induced changes in cell organelles: an ultrastructural study using cadmium sensitive and resistant muntjac fibroblast cell lines

A detailed electron microscopy study of cadmium sensitive and resistant muntjac fibroblast cell lines has identified a wide range of intracellular damage following exposure to cadmium. Damaged organelles included cell membrane, mitochondria, Golgi cisternae and tubular network, chromatin, nucleoli, microfilaments and ribosomes. Although cell membrane damage was generally the earliest indication of adverse cadmium action, particularly with continuous cadmium exposures, cells could tolerate extensive membrane loss. Mitochondrial distortion and some damage to Golgi was also tolerated. The turning point at which cadmium became lethal was generally marked by a cascade of events which included damage to both nuclear and cytoplasmic components. These results for fibroblasts are discussed and compared with damage reported in other types of cells.

The mechanism of cadmium-induced lysozyme enhancement in rabbit kidney

The effect of cadmium on the renal lysozyme level was examined by injecting male albino rabbits subcutaneously with 1 mg cadmium/kg body weight three times a week for 1 or 3 months. The lysozyme level in the renal brush border membrane of the cadmium-treated animals was elevated ten-fold. The lysozyme activity in the liver and small intestine tissue homogenates of rabbits was elevated by a 1-month treatment with cadmium, markedly elevated in the kidney, but markedly reduced in the spleen and lungs. Exposure to cadmium for 3 months produced an essentially similar effect on the enzyme level in the tissue, except for the lungs in which the lysozyme level returned to the preinjection level. This marked increase in the lysozyme level in the kidney of cadmium-treated rabbits was confirmed by an indirect immunofluorescent antibody technique. In control animals, intracellular distribution of the enzyme was selectively distributed to only a small number of proximal tubules, with none distributed in the medulla or glomerulus. However, after expose to cadmium, the renal tubules showed strongly positive lysozyme staining. In addition to an increase in intensity of the specific fluorescence, this enzyme was widely distributed not only in the proximal convoluted portion, but also in the straight portion of the proximal tubules, which essentially showed no enzyme activity under normal conditions. The enzyme in these cells was evenly distributed throughout the cytoplasm. The plasma lysozyme level increased immediately after the administration of cadmium, and detectable amounts of the enzyme began to appear in urine from the 3rd week after the first injection, with a 1-week lag after the maximum level of lysozyme in the plasma. This high level of plasma lysozyme, varied two-to four-fold over the control, and lysozymuria continued throughout the experiment. The concentration of cadmium in the renal cortex was 141 micrograms/g wet tissue at 1 month, and 208 micrograms at 3 months. In conclusion, the cadmium-induced enhancement of the lysozyme level in the renal cortex may be due primarily to the elevation of the lysozyme level in plasma by cadmium. The enzymatic high net positive charge, characteristic of lysozyme, may contribute greatly to this mechanism. In addition, the excretion of a large amount of lysozyme into the urine observed in a later stage may be due to the concomitant occurrence of leakage from the destroyed tubular cells and reduced tubular reabsorption of filtered enzyme, whereas lysozymuria at an early stage may be solely due to excess amounts of plasma lysozyme.

Chronic cadmium intoxication: tissue response in an occupationally exposed patient

This case report describes the natural history of chronic cadmium intoxication in a woman who was exposed to excessive cadmium in her occupation. We document the clinical, laboratory, and tissue response to the toxicant.

Effects of cadmium inhalation on mitochondrial enzymes in rat tissues

Pulmonary and extrapulmonary effects from a 2-h inhalation exposure to cadmium (850 micrograms Cd/m3) were studied in male rats. The effect of this chemical on mitochondrial enzyme activity in the lung, liver, kidney, and testis were investigated immediately after exposure and at 48, 144, and 336 h postexposure. In all tissues studied, mitochondrial citrate synthase activity was significantly increased immediately after the cessation of the exposure. This activity level began to decrease at 48 h postexposure. Succinic dehydrogenase activity was significantly decreased in the lungs and kidney at all periods tested, but increased activity was seen in the liver and testis. Cytochrome c oxidase activity in lungs and testis mitochondria was inhibited at all time periods studied. In the liver and kidney this activity was significantly increased immediately after the exposure ceased, and then a significant reduction began to appear at 48 h postexposure. This study demonstrates that inhaled cadmium, after deposition in the lungs, may alter various enzyme activities in other organs.

Cadmium/zinc relationships in kidney cortex and metallothionein of horse and red deer: histopathological observations on horse kidneys

Cadmium and zinc were determined in kidney cortex of 63 horses and 51 red deer (Cervus elaphus). Cadmium and zinc were also determined in protein fractions obtained by Sephadex chromatography of kidney cortex from 10 horses and 4 red deer. Histopathological parameters in kidney cortex of horses were compared to cadmium content. The metal contents (on wet weight basis) in kidney cortex of the horses were 0.31 +/- 0.22 mmole Cd/kg (range 0.03-1.21) and 0.63 +/- 0.17 mmole Zn/kg (range 0.36-1.23). The Zn content increased with the Cd content, the Zn increase being less at higher concentrations. No significant increase of the Cd content with age of the horses (range 2-19 years) was found. The metal contents in kidney cortex of the red deer were 0.030 +/- 0.031 mmole Cd/kg (range 0.002-0.13) and 0.51 +/- 0.37 mmole Zn/kg (range 0.30-2.82). Here the Zn content did not increase significantly with Cd content, and in this case a positive linear relation of Cd content with age of the deer (range 0-11 years) was observed. The molar Zn/Cd ratio in the metallothionein fractions of horse kidney cortex was less variable at higher Cd contents. All Cd and the increase of Zn above an average basal level of 0.36 mmole Zn/kg was recovered in the metallothionein fractions. No gross histopathological changes could be observed in kidney cortex of the horses. Nevertheless a slight increase of the thickness of the basement membrane of Bowman's Capsule and also of the diameter of Bowman's Capsule in relation to Cd content up to 0.3 mmole/kg could be observed.

Histochemical changes in protein disulphide bonds in rat liver and kidney after chronic cadmium administration, and the possible relation to metallothionein

After chronic exposure to low doses of CdCl2 an increase in disulphide bonds has been established in rat liver using a specific staining method for disulphide bonds and cytophotometric quantitation. This increase is dependent on doses and length of exposure time. Evidence is presented that this increase might be related to the accumulation of metallothionein or some other cadmium binding protein. Using the same staining method after long exposure to low doses of CdCl2 a large number of large dark blue stained granules were observed in the proximal tubule cells, with blue stained deposits in the lumen of the proximal and some renal medulla tubules of the kidney. Evidence is presented that this staining pattern corresponds to the destruction of the proximal tubule cell by the cadmium thionein complex.

Placental toxicity of cadmium in the rat: an ultrastructural study

Pregnant rats on day 18 of gestation were injected s.c. with 40 mumol/kg CdCl2 which caused fetal death and placental necrosis. The placental changes were studied by electron microscopy and indicate that there is a direct placental toxic effect of cadmium which appears targeted at the trophoblast and, in particular, trophoblast cell layer II. Findings in cell layer II which suggest a toxic effect were lysosomal vesiculation, 'buckshot' nuclear chromatin clumping, nucleolar changes and apparent mitochondrial calcification. Furthermore, the selectivity of the effect on cell layer II and the rapidity of the necrosis are also consistent with a toxic effect. Trophoblast cell layer II first undergoes necrosis, but is rapidly followed by the rest of the trophoblast. Many of the changes at this necrotic stage suggest a secondary ischaemic effect or a combined ischaemic and toxic effect. Therefore it appears that cadmium induces placental necrosis via a direct effect on the trophoblast, especially on layer II.

Investigation for the mechanism of cadmium toxicity at cellular level. II. An electron microscopical study

With quantitative techniques at electron microscopical level chromatin condensation and emptying of the interchromatin space have been established in the nuclei of the endothelial cells of small uterine vessels. The nuclear and cytoplasmic changes after cadmium administration show much similarity between endothelial cells of small uterine vessels and cultured liver parenchymal cells. Cytoplasmic changes in both cell types after cadmium administration are suggestive of a disturbance in ribosomal RNA synthesis as the main cause leading to ultimate cell lysis.

Cadmium nephropathy: monitoring for early evidence of renal dysfunction

Prospective studies in humans comparing various tests of cadmium-induced nephropathy have not been reported. Consequently, it is not possible to ascertain which screening methods should be followed in order to detect early nephropathy at a reversible stage. To obtain such data, the authors studied 23 cadmium workers with periodic analyses of blood/urine cadmium levels, hair cadmium content, urinary cytologies, creatinine clearance and urinary levels of lysozyme, beta-2-microglobulins, immunoglobulins, and aminoacids. Blood/urine levels were useful only as indices of acute environmental exposure and not as predictors of total body content or possible nephropathy. Hair content was elevated in most workers. Urine cytology was not reliable. Until further data are available, it is suggested that all five measures of renal function be used in screening and follow-up of cadmium workers for preventing nephropathy.

The chemical form of cadmium in microsomal and mitochondrial fractions from rat liver and kidney after long term administration of cadmium chloride

Wistar rats were given drinking water containing 250 ppm cadmium (Cd) for 12 months. After excising the kidney and liver, the organs were subfractionated into nuclear, mitochondrial, microsomal and cytosol fractions, and the chemical forms of Cd in the subcellular fractions were examined. Although approx. 90% of the total Cd was present in the cytosol, in the form of metallothionein, 3-5% was also present in the mitochondrial fraction and 5-7% in the microsomal fraction from both organs. Each membrane fraction was washed 3 times and there was no contamination of metallothionein from the cytosol according to Cd/protein ratios. By Sephadex G-75 gel filtration, after solubilizing the particulate fractions with sodium deoxycholate, approx. 89% of Cd in the microsomal fraction and 94% in the mitochondrial fraction eluted with the same retention time as that of metallothionein in both liver and kidney, while the remainder was found in a high molecular weight protein fraction. The Cd eluted with the high molecular protein fraction might be involved in dysfunctions in subcellular organelles.

Form of cadmium in rat liver subcellular particle

Cadmium chloride (CdCl2) was injected s.c., 1.5 mg Cd/kg body weight into female Wistar rats for 7 consecutive days. Liver tissue was subfractionated, and ca. 2% of Cd in the tissue was found in the mitochondria and lysosomes, respectively. A high proportion of Cd, in the solubilized mitochondria and lysosomes, was bound to metallothionein and a small amount was distributed to higher molecular weight fraction. Cd in liver mitochondria and lysosomes exists mainly in the form of metallothionein.

Acute effects of cadmium on the spot Leiostomus xanthurus (Teleostei): tissue distribution and renal ultrastructure

Spot (Leiostomus xanthurus) were exposed to 1, 5, 10, 15, and 25 ppm cadmium chloride for 48 h. Analysis by atomic absorption spectrophotometry showed that cadmium accumulated mainly in the liver, followed by heart, gut, kidney, and gill. Brain and body muscle did not concentrate the metal. Electron microscopy showed that the proximal tubule cells were severely affected by cadmium levels of 10, 15, and 25 ppm. The proximal tubule cells exhibited responses that ranged from an increase in heterogeneous bodies to epithelial desquamation. Mitochondria of degenerating proximal tubule cells showed changes similar to metal-poisoned mammalian kidney cells. Some mitochondria were contracted and dense while others were swollen with granular matrices and focal electron densities. In exposures of 25 ppm, Bowman's space of the renal corpuscle was swollen and often contained cellular debris. This study showed that after acute exposure to cadmium the metal accumulated mainly in visceral organs of the spot and at levels of 10 ppm and greater resulted in severe damage to proximal tubule cells of the kidney.

Early signs of oral and inhalative cadmium uptake in rats

Female wistar rats, 170--190 g, were exposed for 90 days to cadmium oxide aerosols containing 25 and 50 microgram Cd/m3 and for 63 days to 100 microgram Cd/m3. Simultaneously female wistar rats, 170--190 g, were fed 25, 50, and 100 ppm cadmium in drinking water for 90 days. After inhalation and ingestion of the metal, there were comparable kidney cadmium levels, but higher liver and blood levels after oral uptake. Coincident with the higher blood cadmium concentrations, proteinuria was observed only after oral administration. Likewise, there was a significant decrease of serum iron after ingestion and no lowering of the serum iron after inhalation of the metal. The inhalation led to a marked dose dependent weight increase of the lungs, which was followed by an impairment of gas exchange. Obviously, after inhalative cadmium uptake of 90 days pulmonary changes precede renal damage.

The biology of cadmium

Industrial exposure to large amounts of cadmium is known to be toxic to man; however, the low levels of cadmium in water, food, and air to which everyone is continually exposed have no obvious effects. During childhood and adolescence, ingestion and inhalation of cadmium are responsible for the average American accumulating about 30 mg of cadmium in his body, with the highest concentration being in the kidney. It has been suggested on the basis of two observations that elevated renal cadmium might be associated with essential hypertension: (1) Hypertensives have been reported to have higher renal cadmium concentrations than normotensives. (2) Long-term exposure to low levels of cadmium has reproducibly caused mild hypertension in animals. Finally, increased levels of cadmium have been found in lungs and other tissues of emphysematous subjects.

The ultrastructural localisation of cadmium

A modified technique for the ultrastructural localisation of heavy metals is described in this paper. The method involves precipitation of heavy metals as sulphides in the tissue by using (NH4)2 S after brief fixation in glutaraldehyde. The sulphides are, in the presence of a physical developer, then used to catalyse the reduction of silver ions into visible molecular silver. This latter step of physical development has been normally carried out after embedding and sectioning. However, when we followed this method we found that the dark metal sulphide was lost from the tissue during the embedding in epoxy resin. Hence the method was unsuitable for our proposed experiment on the ultrastructural localisation of cadmium. We subsequently modified the technique primarily by treating very thin tissue slices with the developer before dehydration and embedding, thus eliminating any problem from sulphide loss. This modified technique was used to investigate the ultrastructural localisation of cadmium in the kidneys of mice which had been exposed to 50 ppm cadmium in their drinking water for up to eight months. The molecular silver was found to be located mainly in the proximal tubule cells, either as dense clumps in apical vesicles and lysosomes or diffuse grains throughout the cytoplasm of the cells particularly in the basal region. We interpret these results as indicating that cadmium is found in the apical vesicles, lysosomes and cytoplasm of proximal tubule cells.

Bone and kidney lesions in experimental cadmium intoxication

Young male rats were fed a diet containing cadmium (0, 10, 30, 100, and 300 ppm) so as to morphologically investigate the relationship between bone and kidney lesions caused by experimental cadmium intoxication. In the early stage of the experiment, before the occurrence of kidney lesions, ingeted cadmium caused osteoporotic changes in bone. In later stages, slight pathologic changes in the kdidney occurred in association with urinary excretion of cadmium. However, there was no evidence of osteomalacic change in bone during the 12-week experimental period. These findings suggest that cadmium may act primarily on bone, rather than secondarily through disturbances of the kidneys, which have some protective ability against cadmium intoxication in the early stage of ingestion of the metal.

Silicon nephropathy

A patient with excessive industrial exposure to silicon and an elevated silicon content in his renal tissue was found to have a distinctive nephropathy, characterized pathologically by changes in the glomeruli and proximal tubules, and manifested clinically by albuminuria and hypertension. Proximal tubular function was intact. From a biochemical standpoint, this finding correlates with the demonstration in vitro that, in contrast to cadmium, a known cause of Fanconi syndrome, silicon does not inhibit renal cortical sodium-potassium-adenosine triphosphatase (Na-K-ATPase).