Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats

Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)₂ quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl₂ aerosol (since Cd²⁺ was present as impurity), 6 h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl₂ were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd²⁺ ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation.     

Cadmium ions influence the chemiluminescence activity of murine splenocytes both in vitro and in vivo

The luminol-enhanced chemiluminescence (CL) activity of splenocytes of mice of the strain (CBA × C57Bl) F₁ was monitored after treatment with Cd²⁺ (cadmium chloride) in both in vitro and in vivo experiments. Cd²⁺ (at concentrations of 1 μM−1 mM) increased the CL reaction of the splenocytes (2 × 10⁶ cells/ml) in vitro in a dose-dependent manner, both instantaneously and after incubation for 1 h. In in vivo experiments. Cd²⁺ was administered in two ways. Following a 14-day administration of cadmium to mice in drinking water (300 mg Cd²⁺/l), the CL reaction of the splenocytes was significantly reduced. On the other hand, after i.p. administration of CdCl₂ dissolved in PBS (2 mg/kg body mass, repeated seven times during 14 days), the metabolic activity of the phagocytes was increased. From the results it follows that cadmium affects the immune system. However, its toxicity is dependent on the route of administration.     

Teratogenic effects and distribution of cadmium (Cd2+) administered via osmotic minipumps to gravid CF-1 mice

Studies to identify the mechanisms underlying the teratogenic effects of cadmium (Cd²⁺) have been complicated by the inherent difficulties of chronically and subchronically administering specific doses of Cd²⁺ to gravid animals under strictly controlled conditions. The objective of the present study was to develop a relatively simple animal model for examining the teratogenic effects of subchronic Cd²⁺ exposure. Cd²⁺ was administered to gravid CF-1 mice by subcutaneously implanted Alzet osmotic minipumps, which released fixed amounts of Cd²⁺ over a 14-day period between days 5 and 18 of gestation. The results showed that Cd²⁺ administered in this manner produced fetal anomalies and that the patterns of Cd²⁺ distribution and the specific developmental defects were similar to those that have been reported for other routes of Cd²⁺ administration. These findings indicate that osmotic minipumps may serve as useful tools in long-term studies of Cd²⁺ teratogenicity. They would appear to be especially useful in teratogenic evaluations where minimizing maternal stress and administering precise doses of Cd²⁺ are important.     

Mechanism of cadmium-induced blockade of neuromuscular transmission

The effect of cadmium ion (Cd²⁺) on neuromuscular transmission was examined in phrenic nerve-diaphragm preparations (PND) of mice and rats.The indirectly induced muscle twitch (IT) was inhibited by Cd²⁺ (0.1–1.0×10^?4M) in a dose-dependent manner, but the directly induced twitch (DT) was rarely affected. The inhibition was reversible and reproducible. An increase in external Ca²⁺ concentration antagonized and an increase in Mg²⁺ concentration potentiated the inhibitory effect of Cd²⁺. The inhibitory effect of Cd²⁺ (2.8×10^?5 M) was antagonized by cysteine (5.6×10^?5 M) applied before or after the Cd²⁺ treatment. Hg²⁺ (mercuric chloride, 2.8×10^?5 M) or p-chloromercuribenzoic acid (PCMB, 2.5×10^?5 M) also inhibited IT but in a different manner. The effects of Hg²⁺ or PCMB were not antagonized by cysteine applied after the treatment. Pretreatment with Hg²⁺ (10^?6 M) or PCMB (5×10^?6 M) did not potentiate the inhibitory effect of Cd²⁺. Resting membrane potential and frequency of miniature end-plate potential (m.e.p.p.) were not affected by Cd²⁺, but m.e.p.p. amplitude was slightly reduced. The end-plate potential was blocked by Cd²⁺ (10^?4 M), and this effect was partially antagonized by an increase in Ca²⁺ concentration. In bioassay experiments, the evoked output of acetylcholine from rat PND was reversibly reduced by Cd²⁺. The inhibitory effect of Cd²⁺ on the output of [¹⁴C]acetylcholine evoked from rat PND was antagonized by an increase in Ca²⁺ concentration and potentiated by an increase in Mg²⁺. From these results, it is suggested that Cd²⁺ reversibly inhibits neuromuscular transmission by reducing transmitter release from motor nerve terminals resulting from the inhibition of Ca²⁺ influx at the membrane of axon terminals. We did not obtain conclusive evidence that Cd²⁺ produces neuromuscular blockade by acting on thiol groups of membrane constituents.     

The effect of salinity on cadmium toxicity to the estuarine mysid Mysidopsis bahia: role of chemical speciation

The effect of salinity on the toxicity of cadmium to the bay mysid, Mysidopsis bahia Molenock, was studied. When toxicity was expressed in terms of free cadmium ion (Cd²⁺) rather than total cadmium (Cd_T), CdCl⁺ or CdCl₂ only a slight salinity effect was apparent, suggesting that Cd²⁺ is the primary toxic species. Mysids were more tolerant of Cd²⁺ at an intermediate salinity of 22‰ and less tolerant at low and high salinity extremes (6 and 38‰). Alteration of cadmium speciation by use of an artificial ligand, nitrilotriacetic acid (NTA), over a range of salinities (14–34‰) produced conflicting results. Toxicity of Cd²⁺ was independent of Cd_T concentration at a given salinity but increased with increasing salinity and/or NTA concentration and was determined to be the result of salinity—Cd²⁺ and NTA-Cd²⁺ interactions. Possible mechanisms of the salinity effect and NTA interaction with cadmium toxicity are discussed.     

Metabolomics comparison of metabolites and functional pathways in the gills of Chlamys farreri under cadmium exposure

The biological processes of Chlamys farreri (C. farreri), an economically important shellfish, are affected when exposed to Cd²⁺. In this study, changes to biological processes and metabolite levels in C. farreri were examined when exposed to Cd²⁺. Ultra-performance liquid chromatography-tandem TOF mass spectrometry (UPLC-TOF/MS)-based untargeted metabolomics was used to examine changes in the metabolism of C. farreri gill tissue exposed to 0.050 mg/L Cd²⁺ for 96 h in a natural environment. Sixty-eight metabolites with significant differences were screened by multivariate statistical analysis. Eleven enriched functional pathways displayed significant changes in inactivity. Differential metabolites, mainly C00157 and C00350, have a significant impact on functional pathways and can be used as potential major biomarkers. Lipid phosphorylation, disruption of signal transduction, and autophagy activation were observed to change in C. farreri when exposed to Cd. The metabolome information supplements research on C. farreri exposure to heavy metals and provides a platform for further multi-omics analysis.     

The potential protective role of lysophospholipid mediators in nephrotoxicity induced by chronically exposed cadmium

Cadmium is a hazardous metal whose chronic exposure induces renal failure due to fibrosis, but the mechanisms are not well known. In this study we analyzed the molecular species of lysophosphatidic acid (LPA) and related phospholipids, together with their metabolic enzyme activity, in plasma from Wistar rats exposed up to 300 ppm Cd²⁺ in drinking water for 114 days. Exposure of 300 ppm Cd²⁺ for 114 days enhanced autotoxin (ATX)/lysophospholipase D activity, but significantly lowered the total levels of LPA and lysophosphatidylethanolamine. Interestingly, the total level of sphingosine-1-phosphate (S1P) was elevated dose-dependently by Cd²⁺. Cultured rat kidney-derived interstitial fibroblast cells, NRK49F cells and proximal epithelial cells, NRK52E cells, were both responsive to the protective action of LPA or S1P against Cd²⁺ toxicity. The former cell expresses ATX RNA. In conclusion, the elevation of LPA-producing enzyme activity and S1P concentrations in plasma after exposure of rats to Cd²⁺ would protect from the renal toxicity of Cd²⁺.     

Effects of Ba2+ and Cd2+ on convulsive electroshock sensitivity and 45Ca distribution in brain subcellular fractions in mice

Barium increases the convulsive corneal electroshock sensitivity of mice tested 0.5 hr after Ba²⁺ administration (6.6 and 20 mg/kg, ip) but decreases sensitivity of mice tested 24 hr after Ba²⁺ (2, 6.6, and 20 mg/kg, ip). Twenty-four hours after Cd²⁺ injection (0.34, 1.1, and 3.4 mg/kg, ip) the percentage of mice convulsing after electroshock was decreased, but 0.5 hr after Cd²⁺ was given no alteration of electroshock sensitivity was seen. Doses of Ba²⁺ and Cd²⁺ which alter electroshock threshold were used to determine effects of these ions on ⁴⁵Ca distribution in subcellular fractions of whole mouse brain. Distribution of Ba and Cd in brain subcellular fractions was also determined. Elevated ⁴⁵Ca in synaptosomes 0.5 hr after Ba²⁺ injection may reflect the ability of Ba²⁺ to cause membrane depolarization and influx of calcium, and these effects may be associated with increased electroshock sensitivity. Increased ⁴⁵Ca in brain synaptosomes was correlated with elevated electroconvulsive shock threshold 24 hr after Cd²⁺ administration. Excess Ca²⁺ in cortical neurons may explain the decreased responsiveness of mice to electroconvulsive shock 24 hr after Cd²⁺ treatment. Accumulation of Ba²⁺ in neurons in the CNS also appears to increase electroconvulsive shock threshold.     

Enzyme biosynthesis versus enzyme activity as a basis for microbial toxicity testing

A toxicity assay based on inhibition of β-galactosidase biosynthesis was compared to a similar assay based on inhibition of β-galactosidase activity. In both tests, Escherichia coli grown in a minimal medium was exposed to isopropyl-β-thiogalactoside to induce β-galactosidase biosynthesis. The induction step preceded contact of cells with the toxicant in the enzyme activity assay, whereas in the enzyme biosynthesis test, the inducer was added following contact of cells with the toxicant. Relative sensitivity was judged on the basis of responses to the heavy metals Hg²⁺, Cu²⁺, and Cd²⁺, and the organics 3,4-dichlorophenol, formaldehyde, Hydrothol, phenol, sodium dodecyl sulphate, and toluene. Comparison of these results to the IC₅₀s achieved with other microbial systems, Daphnia bioassay, and fish bioassay indicates that the enzyme activity test was moderately sensitive to heavy metals but was insensitive to organic toxicants. The test based on inhibition of enzyme biosynthesis was sensitive to both heavy metals and toxic organics.     

Cadmium toxicity in tadpoles of <Emphasis Type="Italic">Rhinella arenarum</Emphasis> in relation to calcium and humic acids

Bioassays were carried out to study the differences in cadmium (Cd) toxicity to premetamorphic tadpoles of Rhinella arenarum, in aqueous solutions with variable contents of calcium in the presence and absence of humic acids, and to analyze the relationship between the free Cd²⁺ ion concentrations calculated by chemical modeling and the biological results. The correlation analysis of the free Cd²⁺ concentration calculated by chemical speciation and the analytical Cd yielded a direct relationship between the degree of toxicity and the slope value. The lowest slope was obtained from the treatments with lowest free Cd²⁺ ion concentration and lowest toxicity, whereas the highest slope was obtained from the most toxic treatment. At comparable concentrations of free Cd²⁺, intralarval Cd increased as the Ca in the solution decreased. At equal contents of Ca, in the presence of humic acids, the content of Cd in larvae was higher and the toxicity values lower. The results obtained in this study show that waterborne Ca could offer some protection from metal uptake and accumulation by competitive inhibition in the uptake mechanism that involves active transport via cell membrane. In the systems with humic materials, a certain proportion of the Cd present in the solution was associated to them and thus became less bioavailable.     

Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: exposure to cadmium

The aims of this study were to (1) evaluate the changes in the Cd tolerance of a marine diatom after exposure under different Cd concentrations for various durations and (2) to explore the potential subcellular and biochemical mechanisms underlying these changes. The 72-h toxicity, short-term Cd uptake, subcellular Cd distribution, as well as the synthesis of phytochelatins (PCs) were measured in a marine diatom Thalassiosira nordenskioeldii after exposure to a range of free Cd ion concentrations ([Cd²⁺], 0.01-84 nM) for 1-15 days. Surprisingly, the diatoms did not acquire higher resistance to Cd after exposure; instead their sensitivity to Cd increased with a higher exposed [Cd²⁺] and a longer exposure period. The underlying mechanisms could be traced to the responses of Cd cellular accumulation and the intrinsic detoxification ability of the preconditioned diatoms. Generally, exposure to a higher [Cd²⁺] and for a longer period increased the Cd uptake rate, cellular accumulation, as well as the Cd concentration in metal-sensitive fraction (MSF) in these diatoms. In contrast, although PCs were induced by the environmental Cd stress (with PC₂ being the most affected), the increased intracellular Cd to PC-SH ratio implied that the PCs’ detoxification ability had reduced after Cd exposure. All these responses resulted in an elevated Cd sensitivity as exposed [Cd²⁺] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.     

Oxidative and osmoregulatory effects of imidacloprid,cadmium, and their combinations on Daphnia magna

Oxidative stress and osmoregulatory system damage-inducing potential of binary mixtures of neonicotinoid insecticide imidacloprid (IMI) and Cd²⁺ in Daphnia magna were evaluated. Animals were subjected to subchronic (7 days) and acute (48 h) of IMI and Cd²⁺ effects with single and binary mixtures. ATPase and antioxidant enzyme activities with lipid peroxidation were measured. Morphometric characteristics were also evaluated. Response patterns showed variability due to the duration, concentration, and toxicant type. While the enzyme activities mostly showed a decreasing trend upon the subchronic IMI effect, there was an increasing trend after the Cd²⁺. Declined enzyme activities were more pronounced with the acute higher IMI+Cd²⁺ exposure. Ca²⁺-ATPase and CAT were the most sensitive biomarkers in the toxicity response. IMI+Cd²⁺ exposures are appeared to increase their toxic effects due to their oxidative potential. ATPase inhibition and antioxidant enzyme alterations with a decrease in morphometric characteristics in Daphnia even at their low concentrations of IMI and Cd²⁺ show evidence of their toxicities on aquatic life. It was emphasized that investigating the combined effects of toxicants at their environmental level based on the multi-biomarker approach is essential in toxicity evaluation.     

New insights into the Ca2+-ATPases that contribute to cadmium tolerance in yeast

Cadmium (Cd²⁺) is a toxic heavy metal which triggers several toxic effects in eukaryotes, including neurotoxicity and impaired calcium metabolism. In the model organism Saccharomyces cerevisiae, the best characterized pathway for Cd²⁺ detoxification involves conjugation with glutathione (GSH) and subsequent transport to vacuoles by Ycf1p, an ATPase homologous to human MRP1 (Multidrug resistance associated protein 1). However, Cd²⁺ tolerance also can be mediated by Pmr1p, a Ca²⁺ pump located in the Golgi membrane, possibly through to the secretory pathway. Herein, we showed that inactivation of the PMR1 gene, alone or simultaneously with YCF1, delayed initial Cd²⁺ capture compared to wild-type (WT) cells. In addition, Cd²⁺ treatment altered the expression profile of yeast internal Ca²⁺ transporters; specifically, PMC1 gene expression is induced substantially by the metal in WT cells, and this induction is stronger in mutants lacking YCF1. Taken together, these results indicate that, in addition to Pmr1p, the vacuolar Ca²⁺-ATPase Pmc1p also helps yeast cells cope with Cd²⁺ toxicity. We propose a model where Pmc1p and Pmr1p Ca²⁺-ATPase function in cooperation with Ycf1p to promote Cd²⁺ detoxification.     

EGCG inhibits Cd2+-induced apoptosis through scavenging ROS rather than chelating Cd2+ in HL-7702 cells

Context and objective: Epigallocatechin-3-gallat (EGCG), the major catechin in green tea, shows a potential protective effect against heavy metal toxicity to humans. Apoptosis is one of the key events in cadmium (Cd²⁺)-induced cytotoxicity. Nevertheless, the study of EGCG on Cd²⁺-induced apoptosis is rarely reported. The objective of this study was to clarify the effect and detailed mechanism of EGCG on Cd²⁺-induced apoptosis.

Methods: Normal human liver cells (HL-7702) were treated with Cd²⁺ for 21?h, and then co-treated with EGCG for 3?h. Cell viability, apoptosis, intracellular reactive oxygen species (ROS), malondialdehyde (MDA), mitochondrial membrane potential (MMP) and caspase-3 activity were detected. On the other hand, the chelation of Cd²⁺ with EGCG was tested by UV-Vis spectroscopy analysis and Nuclear Magnetic Resonance (¹H NMR) spectroscopy under neutral condition (pH 7.2).

Results and conclusion: Cd²⁺ significantly decreased the cell viability and induced apoptosis in HL-7702 cells. Conversely, EGCG co-treatment resulted in significant inhibition of Cd²⁺-induced reduction of cell viability and apoptosis, implying a rescue effect of EGCG against Cd²⁺ poisoning. The protective effect most likely arises from scavenging ROS and maintaining redox homeostasis, as the generation of intracellular ROS and MDA is significantly reduced by EGCG, which further prevents MMP collapse and suppresses caspase-3 activity. However, no evidence is observed for the chelation of EGCG with Cd²⁺ under neutral condition. Therefore, a clear conclusion from this work can be made that EGCG could inhibit Cd²⁺-induced apoptosis by acting as a ROS scavenger rather than a metal chelating agent.     

Cadmium-induced inflammatory responses in cells relevant for lung toxicity: Expression and release of cytokines in fibroblasts,epithelial cells and macrophages

Inhalation is an important route of cadmium (Cd) exposure, and the lung is considered to be one of the main target organs of Cd toxicity. Pulmonary inflammation seems to be involved in development of many lung diseases. In the present study we show that Cd²⁺ at fairly low concentrations affects gene expression of several different cytokines/chemokines in human M1 fibroblasts. The chemokines CXCL2, CXCL3, IL-8/CXCL8 and CCL26, the pro-inflammatory cytokine IL-6 and the receptor IL-1RL1 were expressed at high levels after exposure to 7 μM Cd²⁺ for 7 h. The expression of some important cytokines was further studied in two different primary cell cultures from rat lungs. Cd²⁺ induced cytokine responses at low concentrations (3–6 μM) and early time-points both in type 2 epithelial cell-enriched cultures and alveolar macrophages. However, the two primary lung cells displayed different patterns of cytokine release. Cd²⁺ induced an increased release of IL-6 and MIP-2/CXCL2 from the epithelial cells and MIP-2, IL-1β and TNF-α from alveolar macrophages. In conclusion, the marked up-regulation of different cytokines in these cell types, that are important in development of lung injury and disease, suggests that inflammation may contribute in Cd-induced lung damage.     

Metabolomics approach to study in vivo toxicity of graphene oxide nanosheets

Although graphene oxide (GO) nanosheets are widely used in different fields, the mechanism of their toxicity remains relatively unknown. NMR-based metabolomics was used to study in vivo time and dose-dependent toxicity of GO nanosheets in mice. Sixty serum samples from mice in four different time intervals including 24 and 72 h and 7 and 21 days after injection of 0-, 1-, and 10-mg/kg b.w. were analyzed based on ¹HNMR spectra of each sample and multivariate methods. In comparison with the control group, 12 changed metabolites were identified in GO nanosheet-treated mice groups. These metabolites are involved in steroid hormone biosynthesis and steroid biosynthesis pathways. It was seen that the time factor is more important than the dose factor and the groups were separated in a time direction, completely. We found that GO nanosheets has toxicity and can affect steroidal hormones. However, this study shows that after 21 days, the treated groups regardless of their GO nanosheet dose are very close to the control group. This means that in one step exposure to GO nanosheets, their toxicity diminished after 21 days.     

Cadmium induced oxidative damage and apoptosis in the hepatopancreas of <Emphasis Type="Italic">Meretrix meretrix</Emphasis>

Even trace amounts of cadmium (Cd), a non-essential metal, are known to be toxic to aquatic organisms. Here we investigated the relationship between cadmium ion (Cd²⁺) exposure and oxidative damage and apoptosis in the hepatopancreas of the clam Meretrix meretrix. Clams were exposed to different concentrations of Cd²⁺ (0, 1.5, 3, 6 and 12 mg L^?1) for 5 days. We monitored both antioxidant enzyme activity, including that of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), and levels of malondialdehyde (MDA), glutathione (GSH) and glutathione disulfide (GSSG). Apoptosis of hepatopancreatic cells was detected by DNA laddering and AO/EB double fluorescent staining. The results show that the rate of apoptotis, MDA levels, and caspase-3 activity, increased with Cd²⁺ concentration, whereas GPx activity and the ratio of GSH/GSSG, decreased. SOD and CAT enzyme activity first increased, then decreased, with increasing Cd²⁺ concentration; peak activity of these enzymes was recorded in the 3 mg L^?1 Cd²⁺-treatment group. These results show that Cd-induced oxidative damage can both induce, and aggravate, apoptosis in the hepatopancreatic cells of clams, even at Cd²⁺ concentrations far below the semi-lethal dose for adult clams. The observed changes in caspase-3 activity enhanced significantly at lower Cd²⁺ concentrations, indicating that caspase-3 is a suitable biomarker for heavy metal pollution, especially cadmium pollution, in marine organisms.     

The time-course of cadmium-thionein synthesis in the rat

After the intravenous injection of Cd²⁺ (1.6 mg/kg body wt) the cation accumulates to slightly greater concentrations in the liver and kidneys of the 10-week-old female Wistar rat, than in these organs of the 10-week-old male. Ionic Cd²⁺ is more toxic for the female than for the male, the ld₅₀ values being 1.4 (1.2?1.7) and 2.2 (1.9?2.6) mg Cd²⁺/kg body wt, respectively. This difference in toxicity is not correlated with differences in rates of hepatic cadmium-thionein synthesis. In both sexes, uptake of Cd²⁺ by the liver is complete within 1 hr. In the male rat there is a lag phase of 3–4 hr between the administration of Cd²⁺ and the onset of the induced synthesis of thionein in the liver. Once this synthesis occurs, the content of the metallothionein increases rapidly, Cd²⁺ being transferred to the apoprotein from proteins of high molecular weight that provide the initial binding sites for the cation in the soluble fraction of the liver. At a dose level of 1.6 mg Cd²⁺/kg, synthesis of the metallothionein is mainly complete within 8 hr and appears to be unaffected by age; both the length of the lag phase and subsequent rate of formation of the hepatic metalloprotein in the 80-week-old male rat being the same as those in the 10-week-old animal. In contrast with the male, approximately 5 per cent of the total Cd²⁺ in the soluble fraction of the liver of the female rat is bound as the metallothionein within 1 hr after the administration of the cation. This incorporation of Cd²⁺ into the metalloprotein is attributed to replacement by Cd²⁺ of Zn²⁺ in zinc-thionein, which is present in low concentration in the liver of the normal female rat. This initial replacement is followed by a slow increase in the content of thionein-bound Cd²⁺ during the following 2–3 hr. Thereafter, presumably due to stimulation by the Cd²⁺-induced messenger, the rate of synthesis increases rapidly to a maximum, which is at least equal to, and occurs at the same time, as that in the male. At 24 hr after the administration of Cd²⁺ to the male rat, the content of Zn²⁺ in the hepatic metallothionein is similar to that of Cd²⁺. Replacement of this Zn²⁺ by Cd²⁺ may account for the immediate incorporation of the latter cation into the hepatic metallothionein that occurs when the animals are given a second dose of Cd²⁺. After this initial replacement the synthesis of thionein, which has been primed by the first dose of Cd²⁺, occurs without lag on exposure to the second, and both Zn²⁺ and Cd²⁺ are incorporated into the metallothionein. Intravenous injection of 1.6 mg Cd²⁺/kg body wt also leads to a rapid accumulation of the cation in the kidney, but does not induce the synthesis of the metallothionein in this organ of either the male or female rat during the following 48 hr.