Inhibitory Effect Of Cadmium Research Articles

Inhibitory Effect of Cadmium on the Growth of Mung Bean (Vigna radiata (L.) R. Wilczek) and the Removal by Chelating Agent

This research studied the effect of cadmium (Cd) on the growth of mung bean (Vigna radiata (L.) R. Wilczek). The mung bean was cultured in a Hoagland solution containing different concentrations of Cd (0, 0.1, 0.3 and 0.5 mg/L) for 5 days. The result showed a significant decrease in the lengths of the roots and shoots of mung bean that was grown in cadmium solution. This effect was proportional to the concentrations of Cd. To assess cell death in the root of mung bean, Evan’ s blue staining technique was used in this study. The results showed that the concentrations of Evan's blue dye taken up by Cd-exposed mung beans at 0.1, 0.3, and 0.5 mg/L were 1.5612 ± 0.5417, 6.8641 ± 1.7447, and 8.0850 ± 2.6336 mg/L, respectively. A concentration-dependent increase of dead cellswas found in the Cd-treated group, mostly at the root cap zone. With respect to this result, the level of dead cells that was stained with Evan’s blue dye could be used as a biomarker to indicate cadmium contamination in water. Furthermore, the effects of chelating agents (EDTA) on cadmium removal were also studied. The results showed the possibility of using EDTA as a cadmium treatment agent and promoted plant growth in cadmium contamination areas.

The inhibitory effect of cadmium and/or mercury on soil enzyme activity, basal respiration, and microbial community structure in coal mine–affected agricultural soil

The Cd and Hg contents in soils can be elevated due to coal mining. To estimate the effects of these two heavy metals on soil enzymes and the key microbial groups, coal mine–affected agricultural soils were cultured for 30 days with Cd and/or Hg. Soil enzyme activities were measured by a colorimetric method, and microbial abundance was assessed according to real-time quantitative PCR analysis of the 16S rRNA and 18S rRNA genes. In addition, the microbial communities were analyzed by Illumina sequencing. Heavy metals inhibited soil enzyme activities. For example, both Cd and Hg decreased 25.52–34.89% of the soil catalase activity; the highest level of Hg (30 mg kg−1) decreased 76.50–89.88% of the soil urease activity and 85.60–92.92% of the soil dehydrogenase activity; and the soil acid phosphatase activity significantly decreased by 15.18–32.64% under all the levels of Cd and decreased 17.09–30.32% under the high levels of the Cd–Hg combination (> 3 mg kg−1). In addition, increased Cd levels affected bacterial number more than fungal abundance; however, addition of Hg alone decreased the bacterial number but increased the fungal abundance. Furthermore, the bacterial communities but not fungal communities were altered by heavy metals. A total of 23 highly sensitive genera and 16 highly resistant genera were identified. The sensitive genera were assigned to Actinobacteria, Acidobacteria, Candidate division WS3, Chloroflexi, Gemmatimonadetes, Proteobacteria, and Thermotogae, while the resistant genera were affiliated to Bacteroidetes and Proteobacteria. Soils containing the highest level of the combination of Cd and Hg exhibited the lowest soil enzyme activities; bacterial communities were more sensitive to heavy metal contamination than fungi.

Reduced Activity of Nitrate Reductase Under Heavy Metal Cadmium Stress in Rice: An in silico Answer.

Cadmium is a well known toxic heavy metal, which has various detrimental effects on plant system. In plants an important enzyme involved in the production of nitric oxide, nitrate reductase, is also affected by cadmium toxicity. According to many studies cadmium has an inhibitory effect on nitrate reductase activity. Similar effect of cadmium was found in our study where an inhibitory effect of cadmium on nitrate reductase activity was noted. However, the mechanism behind this inhibition has not been explored. With the help of homology, 3-D structure of rice-nitrate reductase is modeled in this study. Its binding with nitrate, nitrite and cadmium metal in silico has been explored. The bonds formed between the enzyme-substrate complex, enzyme-cadmium and differences in interactions in presence of cadmium has been studied in detail. The present study should help in understanding the modeled structure of rice-nitrate reductase in 3-D which may in turn guide enzyme related studies in silico. The present study also provides an insight as to how cadmium interacts with nitrate reductase to alter the enzyme activity.

Inhibitory effect of cadmium(II) ion on anodic electrochemically active biofilms performance in bioelectrochemical systems

Cadmium(II) ion can affect the anode performance of bioelectrochemical systems (BES); however, how the presence of Cd2+ affect the extracellular electron transfer of anodic electrochemically active biofilms (EABs), the microbial viability and species composition of microorganism on the anode remain poorly understood. Here, we investigated the inhibitory effect of Cd2+ at different concentrations on the electrochemical performance and the biofilm community in mixed-culture enriched BES. The electrochemical performance of the BES was not inhibited at 2 mg L−1 Cd2+, while higher concentrations of 5–20 mg L−1 resulted in the decrease in the maximum power density, with 0.34 ± 0.01 W m−2 at 5 mg L−1, 0.28 ± 0.01 W m−2 at 10 mg L−1, and 0.17 ± 0 W m−2 at 20 mg L−1, respectively. When adding 30 mg/L Cd2+, there was almost no power output. The decline of the power output was possibly ascribed to the suppressed viability and the change of species richness as evident from confocal laser scanning microscopy and microbial community analysis. Cyclic voltammogram and electrochemical impedance spectroscopy revealed that high concentration of Cd2+ exceeding 5 mg L−1 can inhibit the secretion of outer membrane cytochromes, thus reducing the electron transfer between the EABs and the anode surface. Analysis of bacterial structures showed a decrease in Geobacter accompanied by an increase in Stenotrophomonas and Azospira in response to Cd2+ at 10 and 20 mg L−1. This study added to the in-depth analysis of the inhibition of Cd2+ on EABs, and provided new insights into the removing Cd2+ and organics simultaneously in BES.

Improved ethanol production in the presence of cadmium ions by a Saccharomyces cerevisiae transformed with a novel cadmium-resistance gene DvCRP1

ABSTRACTThe DvCRP1 gene obtained from Dunaliella viridis is a cadmium-resistance gene that induces cadmium accumulation in microbial and plant cells. In the present study, Saccharomyces cerevisiae was used as a model system to investigate the effect of DvCRP1 on both cadmium detoxification and ethanol production. Inhibitory effects of cadmium (50–300 µmol/L) on growth (29–92%), glucose consumption (23–89%), and ethanol production (17–92%) were observed at 24 h by S. cerevisiae. DvCRP1 alleviated the inhibitory effect of cadmium, with increase in the ethanol production. The established mathematical model showed that the initial inoculation concentration, cadmium concentration, and transformation of DvCRP1 were the most important factors for cell growth, glucose consumption, and ethanol production. Cadmium detoxification of yeast was also enhanced by increasing the initial concentration of yeast cells. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations. Transforming with DvCRP1 further enhanced detoxification, especially at high cadmium concentrations (200 µmol/L). The present results evidenced the potential of the insertion of the DvCRP1 gene into yeast for use in bio-refineries during fermentation of heavy metals-contaminated substrates. In addition, this is a promising method for phytoremediation of agricultural soils highly contaminated by heavy metals.

Inhibitory effect of cadmium on estrogen signaling in zebrafish brain and protection by zinc

The present study was conducted to assess the effects of Cd exposure on estrogen signaling in the zebrafish brain, as well as the potential protective role of Zn against Cd-induced toxicity. For this purpose, the effects on transcriptional activation of the estrogen receptors (ERs), aromatase B (Aro-B) protein expression and molecular expression of related genes were examined in vivo using wild-type and transgenic zebrafish embryos. For in vitro studies, an ER-negative glial cell line (U251MG) transfected with different zebrafish ER subtypes (ERα, ERβ1 and ERβ2) was also used. Embryos were exposed either to estradiol (E2 ), Cd, E2 +Cd or E2 +Cd+Zn for 72 h and cells were exposed to the same treatments for 30 h. Our results show that E2 treatment promoted the transcriptional activation of ERs and increased Aro-B expression, at both the protein and mRNA levels. Although exposure to Cd, does not affect the studied parameters when administered alone, it significantly abolished the E2 -stimulated transcriptional response of the reporter gene for the three ER subtypes in U251-MG cells, and clearly inhibited the E2 induction of Aro-B in radial glial cells of zebrafish embryos. These inhibitory effects were accompanied by a significant downregulation of the expression of esr1, esr2a, esr2b and cyp19a1b genes compared to the E2 -treated group used as a positive control. Zn administration during simultaneous exposure to E2 and Cd strongly stimulated zebrafish ERs transactivation and increased Aro-B protein expression, whereas mRNA levels of the three ERs as well as the cyp19a1b remained unchanged in comparison with Cd-treated embryos. In conclusion, our results clearly demonstrate that Cd acts as a potent anti-estrogen in vivo and in vitro, and that Cd-induced E2 antagonism can be reversed, at the protein level, by Zn supplement. Copyright © 2016 John Wiley & Sons, Ltd.

Use of a thermoresponsive polymer in ethanol fermentation carried out in a cadmium-containing medium

In this study, a new thermoresponsive polymer, PG1-co-PHEDTA, was used as a reagent for the detoxification and recovery of cadmium from ethanol fermentation carried out in a cadmium-containing medium. We found that the polymer, PG1-co-PHEDTA, had an important role in ethanol production. In the absence of PG1-co-PHEDTA, ethanol fermentation was severely inhibited by cadmium. However, the inhibitory effect of cadmium could be significantly alleviated by the addition of PG1-co-PHEDTA, and the rates of glucose consumption and ethanol production were similar to those reported for cadmium-free fermentation processes. The investigation into the key units of PG1-co-PHEDTA showed that HEDTA was the contributing factor for the positive effect on ethanol fermentation. However, the effect of HEDTA that was incorporated into PG1 was higher than that of the free HEDTA. Three-fold higher concentration of free HEDTA was required to obtain similar results as that with PG1-co-PHEDTA additive. Glutathione (GSH) and cadmium assays demonstrated that the transport of cadmium into the cell could be prevented by PG1-co-PHEDTA via the formation of a chelated structure with the HEDTA groups in PG1-co-PHEDTA. By applying the unique phase transition of PG1-co-PHEDTA, cadmium of more than 90% could be removed from fermentation broths with a simple centrifugation step.

Kinesin-dependent motility generation as target mechanism of cadmium intoxication

The anterograde vesicle transport within neurons critically depends on microtubules and on the activity of kinesin. The present study demonstrates that cadmium ions inhibit the in vitro assembly of microtubules from tubulin, whereby at high cadmium levels (∼500μM) unstructured protein aggregates were formed. Cadmium ions also significantly lower both the ATPase and motility activity of neuron-specific kinesin KIF5A in concentration-dependent manner. For the inhibition of KIF5A ATPase activity, an IC50 value of 10.4±1.5μM was determined. Inhibition could be widely compensated by addition of EGTA, but not by addition of thiols. The inhibitory effect of cadmium on KIF5A was considerably weakened by increasing ATP concentration. As nucleoside triphosphate binding is known to be accompanied by conformational changes within the kinesin motor domain, it might be suggested that these changes protect the motor domain against cadmium. The effects of cadmium ions on the kinesin–microtubule motility generating system are considered to contribute to the development of neuronal disorders caused by cadmium intoxication.

Tubulin posttranslational modifications induced by cadmium in the sponge Clathrina clathrus

As sessile filter feeders, sponges are exposed to environmental stress due to pollutants of both anthropogenic and natural origins and are able to accumulate harmful substances. Thus, sponges are considered a good tool for the biomonitoring of coastal areas. In this study, we used biochemical and immunocytochemical analyses to provide new data on the cadmium-related changes in sponge cells. In particular, we analyzed the effects of different concentrations of cadmium on the microtubule network in the calcisponge Clathrina clathrus. Quantitative densitometry of the immunoblots showed that, while the levels of α- and β-tubulin remained relatively constant in C. clathrus when exposed to 1 and 5μM CdCl2, there were progressive shifts in the levels of some tubulin isoforms. Exposure for 24h to sublethal concentrations of cadmium reduced the level of tyrosinated α-tubulin and enhanced the levels of acetylated and detyrosinated α-tubulin relative to the levels in controls. Confocal microscopy analysis of immunolabeled tissue sections showed that the inhibitory effect of cadmium was associated with a decrease in the labeling of the cells with a monoclonal antibody that recognizes tyrosinated α-tubulin. By contrast, the reactivity with a monoclonal antibody that recognizes acetylated α-tubulin and with a polyclonal antibody specific for detyrosinated α-tubulin was enhanced at the same time points. Because the acetylation and detyrosination of α-tubulin occur on stable microtubules, the marked enhancement of α-tubulin acetylation and detyrosination in Cd2+-treated cells indicates that divalent Cd ions stabilize microtubules. The possibility that Cd2+ may increase the stability of cytoplasmic microtubules was tested by exposing Cd2+-treated cells to a cold temperature (0°C). As shown, the microtubule bundles induced by Cd2+, which were labeled by the monoclonal antibodies against acetylated and detyrosinated α-tubulin, were resistant to cold.

Cadmium Removal by the Hydroponic Culture of Giant Reed (Arundo donax) and Its Concentration in the Plant

Giant reed has high biomass productivity, and is a promising plant to be used for a constructed wetland system in which energy/material production and water purification are achieved simultaneously (multi-functional wetland). In this study, the cadmium removal by hydroponically cultured giant reed was observed, and its concentration in the plant body was measured to clarify the applicability of the wetland for cadmium treatment. The results suggested that the hydroponic culture of giant reed has high potential for cadmium removal. In addition, the inhibitory effect of cadmium on phosphorus removal, that is also important for water purification, was not observed under a concentration lower than 1 mg-Cd/L for 7 days. After about 2 months of hydroponic culture the absorbed cadmium was highly concentrated in the rhizome. Furthermore, the positive correlation between glutathione (GSH) in the rhizome and cadmium removal rate was observed, indicating that the production of GSH was controlled by the cadmium assimilated in the giant reed.

Cadmium Regulates the Expression of the CFTR Chloride Channel in Human Airway Epithelial Cells

Cadmium is a toxic heavy metal ranked seventh on the Priority List of Hazardous Substances. As a byproduct of smelters, cadmium is a prevalent environmental contaminant. It is also a major component of cigarette smoke, and its inhalation is associated with decreased pulmonary function, lung cancer, and chronic obstructive pulmonary disease. Ion channels, including the cystic fibrosis transmembrane conductance regulator (CFTR), play a central role in maintaining fluid homeostasis and lung functions. CFTR is mostly expressed in epithelial cells, and little is known about the effect of cadmium exposure on lung epithelial cell function. We show that exposure to cadmium decreases the expression of the CFTR protein and subsequent chloride transport in human airway epithelial cells in vitro. Impairment of CFTR protein expression was also observed in vivo in the lung of mice after intranasal instillation of cadmium. We established that the inhibitory effect of cadmium was not a nonspecific effect of heavy metals, as nickel had no effect on CFTR protein levels. Finally, we show that selected antioxidants, including alpha-tocopherol (vitamin E), but not N-acetylcysteine, can prevent the cadmium-induced suppression of CFTR. In summary, we have identified cadmium as a regulator of the CFTR chloride channel present in lung epithelial cells. Future strategies to prevent the deleterious effect of cadmium on epithelial cells and lung functions may benefit from the finding that alpha-tocopherol protects CFTR expression and function.

Inhibitory effect of cadmium on clock gene expressions

Inhibitory effect of cadmium on clock gene expressions

Degradative Plasmid and Heavy Metal Resistance Plasmid Naturally Coexist in Phenol and Cyanide Assimilating Bacteria

Problem statement: Heavy metals are known to be powerful inhibitors of xenobiotics biodegradation activities. Alleviation the inhibitory effect of these metals on the phenol biodegradation activities in presence of heavy metals resistant plasmid was investigated. Approach: Combination of genetic systems of degradation of xenobiotic compound and heavy metal resistance was one of the approaches to the creation of polyfunctional strains for bioremediation of soil after co-contamination with organic pollutants and heavy metals. Results: A bacterial strain Pseudomonas putida PhCN (pPhCN1, pPhCN2) had been obtained. This bacterium contained two plasmids, a 120 Kb catabolic plasmid that encode for breakdown of phenol (pPhCN1) and pPhCN2 plasmid (100 Kb) that code for cadmium and copper resistant. Cyanide assimilation by this bacterium was encoded by chromosomal genes. The inhibitory effect of cadmium (Cd2+) or copper (Cu2+) on the degradation of phenol and cyanide by P. putida strains PhCN and PhCN1 (contained pPhCN1) were investigated. The resistant strain PhCN showed high ability to degrade phenol and cyanide in presence of Cd2+ or Cu2+ comparing with the sensitive strain PhCN1. In addition, Cd2+ or Cu2+ was also found to exert a strong inhibitory effect on the C23O dioxygenase enzyme activity in the presence of cyanide as a nitrogen source. Conclusion: The presence of heavy metal resistance plasmid alleviated the inhibitory effect of metals on the phenol and cyanide assimilation by resistant strain.

APPLICATION OF STATISTICAL EXPERIMENTAL DESIGN AND MULTIVARIATE DATA ANALYSIS FOR EVALUATION OF MIXTURES USING CYTOCHROME P4501A INDUCTION

Cytochrome P4501A (CYP1A) induction was evaluated in the rat hepatoma cell line H4IIE as a biomarker of exposure to organic compounds. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide assay was performed to assess the viability of cells exposed to environmentally relevant concentrations of cadmium. Cadmium concentrations greater than approximately 0.7 microM were found to affect cell viability. Cells were exposed to environmentally relevant concentrations of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) or benzo[a]pyrene (BaP) and to combinations of PCB 77, BaP, and cadmium based on a statistical experimental design. Quantification of CYP1A proteins using Western blot analysis showed that both BaP and PCB 77 induced CYP1A in a concentration-dependent manner up to 5 microM. Response surface modeling for evaluation of the combined effect of compounds was conducted using the multivariate regression model projection to latent structures (PLS). Analysis of response surface models for the ternary mixtures indicated antagonistic interactions between BaP and PCB 77 and a possible inhibitory effect of cadmium on PCB 77- induced CYP1A. Use of CYP1A induction in the H4IIE cell line with immunodetection of CYP1A proteins, combined with the application of response surface design and PLS, is shown to be a suitable strategy for evaluating combined effects in pollutant mixtures.

Application of Statistical Experimental Design and Multivariate Data Analysis for Evaluation of Mixtures using Cytochrome P4501A Induction

Cytochrome P4501A (CYP1A) induction was evaluated in the rat hepatoma cell line H4IIE as a biomarker of exposure to organic compounds. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide assay was performed to assess the viability of cells exposed to environmentally relevant concentrations of cadmium. Cadmium concentrations greater than approximately 0.7 microM were found to affect cell viability. Cells were exposed to environmentally relevant concentrations of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) or benzo[a]pyrene (BaP) and to combinations of PCB 77, BaP, and cadmium based on a statistical experimental design. Quantification of CYP1A proteins using Western blot analysis showed that both BaP and PCB 77 induced CYP1A in a concentration-dependent manner up to 5 microM. Response surface modeling for evaluation of the combined effect of compounds was conducted using the multivariate regression model projection to latent structures (PLS). Analysis of response surface models for the ternary mixtures indicated antagonistic interactions between BaP and PCB 77 and a possible inhibitory effect of cadmium on PCB 77- induced CYP1A. Use of CYP1A induction in the H4IIE cell line with immunodetection of CYP1A proteins, combined with the application of response surface design and PLS, is shown to be a suitable strategy for evaluating combined effects in pollutant mixtures.

Effect of heavy metals on the biodegradation of dibenzofuran in liquid medium

The effect of heavy metals on the degradation of dibenzofuran by Sphingomonas wittichii RW1 was determined in liquid cultures. The results showed that 10 mg/L cadmium, mercury and copper not only affected the growth of RW1 with dibenzofuran but also the ability of resting cells to degrade this compound. Growth and degradation were strongly inhibited by mercury, even at 1 mg/L, while the inhibitory effect of cadmium and copper at the same concentration or at 5 mg/L were negligible. In contrast, arsenic and lead did not affect degradation or growth, even at very high concentrations of 100 mg/L. Subsequent analyses additionally revealed that concentrations of arsenic and lead remained unchanged following incubation, while those of cadmium, mercury and copper decreased significantly.

Possible role of glutamate, aspartate, glutamine, GABA or taurine on cadmium toxicity on the hypothalamic pituitary axis activity in adult male rats.

This work was designed to evaluate the possible changes in glutamate, aspartate, glutamine, GABA and taurine within various hypothalamic areas the striatum and prefrontal cortex after oral cadmium exposure in adult male rats, and if these changes are related to pituitary hormone secretion. The contents of glutamine, glutamate, aspartate, GABA and taurine in the median eminence, anterior, mediobasal and posterior hypothalamus, and in prefrontal cortex in adult male rats exposed to 272.7 micromol l(-1) of cadmium chloride (CdCl2) in the drinking water for one month. Cadmium diminished the content of glutamine, glutamate and aspartate in anterior hypothalamus as compared to the values found in the untreated group. Besides, there is a decrease in the content of glutamate, aspartate and taurine in the prefrontal cortex. The amino acids studied did not change in median eminence, mediobasal and posterior hypothalamus or the striatum by cadmium treatment. Plasma prolactin and LH levels decreased in rats exposed to the metal. These results suggest that (1) cadmium differentially affects amino acid content within the brain region studied and (2) the inhibitory effect of cadmium on prolactin and LH secretion may be partially explained by a decrease in the content of both glutamate and aspartate in anterior hypothalamus, but not through changes in GABA and taurine.

Effect of cadmium, mercury and copper on partially purified hepatic flavokinase of rat.

The effect of cadmium (Cd2+), mercury (Hg2+) and copper (Cu2+) was studied with partially purified flavokinase (ATP:riboflavin 5'-phosphotransferase EC 2.7.1.26) from rat liver. All the divalent heavy metal cations inhibited flavokinase activity in a concentration-dependent manner. The inhibitory effect of cadmium on the enzyme was completely reversed by increasing concentration, of Zinc (Zn2+) indicating a competition between Zn2+ and Cd2+ for binding with the enzyme. A competition between riboflavin and Cd2+ is also evident from the present investigation. These observations hint at the possibility that Zn2+ and Cd2+ probably compete for the same site on the enzyme where riboflavin binds. However, inhibition of flavokinase by Hg2+ could not be reversed by Zn2+. Our studies further reveal that hepatic flavokinase appears to contain an essential, accessible and functional thiol group(s) which is evident from a concentration dependent inhibition of activity by sulfhydryl reagents like parachloromercuribenzoate (PCMB), 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB), and N-ethylmaleimide (NEM). Inhibition of flavokinase by sulfhydryl reagents were protected, except in case of NEM inhibition, when the enzyme was incubated with thiol protectors like glutathione (GSH) and dithiothreitol (DTT). Furthermore, the enzyme could also be protected from the inhibitory effect of Cd2+ and Hg2+ by GSH and DTT suggesting that Cd2+ probably interacts with a reactive thiol group at or near the active site of enzyme in bringing about its inhibitory effect.

Effect of cadmium on the ligninolytic activity ofStereum hirsutum andPhanerochœte chrysosporium

An inhibitory effect of cadmium on the growth and ligninolytic activity of the wood-rotting basidiomycetesPhanerochœte chrysosporium, Pleurotus ostreatus, Pycnoporus cinnabarinus andStereum hirsutum was observed. Delayed decolorization of the polymeric dye Poly R-478 was observed in samples with 0.10 mmol/L Cd. Addition of 0.25 mmol/L Cd to the cultivation medium strongly reduced the activity of both Mn-dependent and Mn-independent peroxidases ofStereum hirsutum, while the activity of laccase was not affected to a similar extent. The maximum of MnP activity in these samples was found during the exponential phase of growth whereas control samples showed the highest activity after the onset of the stationary phase (days 15–21). Cadmium at concentrations higher than 0.50 mmol/L significantly inhibited the activity of all enzymes tested in bothS. hirsutum andP. chrysosporium.

Calcium-cadmium interaction on sugar absorption across the rabbit jejunum.

The element Cd is considered to have no biological function and is highly toxic to humans and animals. Toxic effects of this metal upon cell membrane structure and function have been shown. On the other hand, Ca is an essential element in a wide variety of cellular activities. The present study was initiated to research whether the interaction between Ca and Cd could affect D-galactose absorption across the rabbit jejunum in vitro. In media with Ca2+, when CdCl2 was present at 0.5 or 1 mM, Cd was found to significantly reduce the sugar absorption. In Ca2+ -free media, where CaCl2, was omitted and replaced isotonically with choline chloride, the sugar transport was not modified by Cd, but when CaCl2 was replaced isotonically with MgCl2, the inhibition is observed. Verapamil at 10(-6)M (blocking mainly Ca2+ transport) did not modify the inhibitory effect of cadmium on D-galactose transport. When 10(-6)M of A 23187 (Ca2+ specific ionophore) was added in media with/without Ca2+; CdCl2 produced no change in D-galactose transport. These results suggest that Ca and Cd could have affinity for the same chemical groups of enterocyte membrane, which would be related with the intestinal absorption of D-galactose.