Effectiveness of ZnCl2 in protecting against nephrotoxicity induced by HgCl2 in newborn rats

Current Progress in Gallium-based Liquid Metals for Combinatory Phototherapeutic Anticancer Applications

A variety of therapeutic approaches using liquid metal (LM) have been intensively investigated, due to its unique physico-chemical properties that include high surface tension, fluidity, shape deformability, thermal conductivity, and electrical conductivity. Among a series of LMs, the relatively lower toxicity and minimal volatility of gallium (Ga)-based LMs (GaLMs) enables their usage in a series of potential biomedical applications, especially implantable platforms, to treat multiple diseases. In addition, the highly efficient conversion of light energy into thermal or chemical energy via GaLMs has led to recent developments in photothermal and photodynamic applications for anticancer treatments. As attractive photothermal agents or photosensitizers, a systematic interpretation of the structural characteristics and photo-responsive behaviors of GaLMs is necessary to develop effective anticancer engineering applications. Therefore, the aim of this review is to provide a comprehensive summary of currently suggested GaLM-mediated photo-therapeutic cancer treatments. In particular, the review summarizes (1) surface coating techniques to form stable and multifunctional GaLM particulates, (2) currently investigated GaLM-mediated photothermal and photodynamic anticancer therapies, (3) synergistic efficacies with the aid of additional interventions, and (4) 3D composite gels embedded with GaLMs particles, to convey the potential technological advances of LM in this field.

Biochemical Parameters of Female Wistar Rats and Their Offspring Exposed to Inorganic Mercury in Drinking Water during the Gestational and Lactational Periods

The aim of this study was to investigate the effects of inorganic mercury (Hg²⁺) exposure on biochemical parameters of dams and their offspring exposed to metal in drinking water. Female Wistar rats were exposed to 0, 10, and 50 µg Hg²⁺/mL (as HgCl₂) for 42 days corresponding to gestational (21 days) and lactational (21 days) periods. The offspring were sacrificed on postnatal days 10, 20, 30, and 40. Dams exposed to Hg²⁺ presented a decrease in water intake in gestation [total: F(2,19) = 15.84; p ≤ 0.0001; daily: F(2,21) = 12.71; p = 0.0002] and lactation [total: F(2,19) = 4.619; p = 0.024; daily: F(2,21) = 5.309; p = 0.0136] without alteration in food intake. Dams exposed to 50 µg Hg²⁺/mL had an increase in kidney total [F(2,21) = 8.081; p = 0.0025] and relative [F(2,21) = 14.11; p = 0.0001] weight without changes in biochemical markers of nephrotoxicity. Moreover, dams had an increase in hepatic [F(2,10) = 3.847; p = 0.0577] and renal [F(2,11) = 6.267; p = 0.0152] metallothionein content concomitantly with an increase in renal Hg levels after Hg²⁺ exposure. Regarding offspring, the exposure to Hg²⁺in utero and breast milk increased the relative liver [F(2,18) = 5.33; p = 0.0152] and kidney [F(2,18) = 3.819; p = 0.0415] weight only on the postnatal day 40. In conclusion, dams were able to handle the Hg²⁺ avoiding the classic Hg²⁺ toxic effects as well as protecting the offspring. We suggest that this protection is related to the hepatic and renal metallothionein content increase.

In vivo evaluation of the potential protective effects of prolactin against damage caused by methylmercury

Non-biodegradable metals such as mercury accumulate in living organisms during life (bioaccumulation) and also within trophic webs (biomagnification) and may reach high concentrations in humans. The contamination of humans by mercury in drinking water and food may be common, in particular in riverside communities that have a diet rich in fish. In vitro studies of human cell lines exposed to the cytotoxic and mutagenic effects of methylmercury have shown that prolactin has potential cytoprotective properties and may act as a co-mitogenic factor and inhibitor of apoptosis. The present in vivo study investigated the protective potential of prolactin against the toxic effects of methylmercury in the mammal Mus musculus. Histological and biochemical analyses, together with biomarker of genotoxicity, were used to verify the protective potential of prolactin in mice exposed to methylmercury. The reduction in kidney and liver tissue damage was not significant. However, results of biochemical and genotoxic analyses were excellent. After prolactin treatment, a significant reduction was observed in biochemical parameters and mutagenic effects of methylmercury. The study results therefore indicated that prolactin has protective effects against the toxicity of methylmercury and allowed us to suggest the continuation of research to propose prolactin in the future, as an alternative to prevent the damage caused by mercury, especially in populations that are more exposed.

Unravelling the interactive effect of soil and atmospheric mercury influencing mercury distribution and accumulation in the soil-rice system

Mercury (Hg) accumulation in rice is an emerging health concern worldwide. However, sources and interactions responsible for Hg species accumulation in different rice tissues are still uncertain. Four experimental plots were carefully designed at an artisanal Hg mining site and a control site to evaluate the effect of atmospheric and soil Hg contents on Hg accumulation in rice. We showed that inorganic Hg (IHg) contents in rice tissues grown either in contaminated or control site soil (non-contaminated soil) were higher at Hg artisanal mining site than those at the control site. Elevated total gaseous mercury (TGM) levels in ambient air were the predominant source of IHg to rice at the Hg mining area. Methylmercury (MeHg) concentrations in rice plant tissues increased in proportionality with MeHg contents in paddy soil. Our results suggest that both atmosphere and soil Hg sources have been impacted the IHg accumulation in rice. Above ground rice tissues, grains, leaves, and stalk accumulated IHg from both atmosphere and soil to varying degrees. Nonetheless, the study also provides the first direct evidence that atmospheric Hg accumulated by above-ground rice tissues could be translocated to below-ground tissues (roots). However, the extent to which atmosphere or soil Hg contributes to IHg in rice tissues may vary with each source's concentration gradient at the given site. No evidence of in planta Hg methylation was found during the current study. Hence, paddy fields are potential MeHg production sites, whereas paddy soil is a unique MeHg accumulation source in rice plants. This study expands and clarifies the contribution of various sources involved in Hg accumulation in the soil rice system. The findings here provide the basis for future research strategies to deal with the global issue of Hg contaminated rice.

The human health risks assessment of mercury in soils and plantains from farms in selected artisanal and small-scale gold mining communities around Obuasi, Ghana

Food consumption remains the commonest pathway through which humans ingest higher levels of mercury (Hg). Long-term exposure to Hg through Hg-contaminated food may result in acute or chronic Hg toxicity. Incessant discharge of Hg waste from ASGM facilities into nearby farms contaminates food crops. Ingestion of such food crops by residents may lead to detrimental human health effects. The human health risks upon exposure to total mercury (THg) and methylmercury (MeHg) in farmland soils and plantains from farms sited near ASGM facilities were studied in four communities around Obuasi, Ghana. The human health risk assessment was evaluated using hazard quotient (HQ), estimated average daily intake (_e AvDI), hazard index (HI) and Hg elimination and retention kinetics. Tweapease, Nyamebekyere and Ahansonyewodea had HQ, _e AvDI and HI for THg of plantains for both adults and children below the recommended USEPA limit of 1, 3 × 10^-4  mg/kg/day and 1, respectively. Odumase had HQ, _e AvDI and HI for THg of plantains for both adults and children, higher than the guideline values. This meant that only Odumase may cause non-carcinogenic human health effects upon repeated exposure. The HQ, _e AvDI and HI values of MeHg for all the study areas were far below guideline values, hence may not pose any non-carcinogenic human health risks to residents even upon repeated exposure. Retention and elimination kinetics of Hg also showed that only plantains from Odumase may pose significant non-carcinogenic human health risks to residents because the final amount of inorganic mercury exceeded the extrapolated USEPA guideline value of 0.393 μg/kg/year.

Transcriptome Analysis Reveals HgCl2 Induces Apoptotic Cell Death in Human Lung Carcinoma H1299 Cells through Caspase-3-Independent Pathway

Mercury is one of the detrimental toxicants that can be found in the environment and exists naturally in different forms; inorganic and organic. Human exposure to inorganic mercury, such as mercury chloride, occurs through air pollution, absorption of food or water, and personal care products. This study aimed to investigate the effect of HgCl₂ on cell viability, cell cycle, apoptotic pathway, and alters of the transcriptome profiles in human non-small cell lung cancer cells, H1299. Our data show that HgCl₂ treatment causes inhibition of cell growth via cell cycle arrest at G₀/G₁- and S-phase. In addition, HgCl₂ induces apoptotic cell death through the caspase-3-independent pathway. Comprehensive transcriptome analysis using RNA-seq indicated that cellular nitrogen compound metabolic process, cellular metabolism, and translation for biological processes-related gene sets were significantly up- and downregulated by HgCl₂ treatment. Interestingly, comparative gene expression patterns by RNA-seq indicated that mitochondrial ribosomal proteins were markedly altered by low-dose of HgCl₂ treatment. Altogether, these data show that HgCl₂ induces apoptotic cell death through the dysfunction of mitochondria.

Mercury toxicity in pregnant and lactating rats: zinc and N-acetylcysteine as alternative of prevention

This study evaluated the toxic effects of inorganic mercury (Hg) in pregnant and lactating rats, as well as the possible protective effect of zinc (Zn) and N-acetylcysteine (NAC). Pregnant and lactating rats were pre-treated with ZnCl₂ (27 mg/kg) and/or NAC (5 mg/kg) and after 24 h, they were exposed to HgCl₂ (10 mg/kg). Animals were sacrificed 24 h after Hg exposure, and biochemical tests and metal determination were performed. Regarding pregnant rats, Hg exposure caused kidney, blood, and placenta δ-aminolevulinic acid dehydratase (δ-ALA-D) activity inhibition, and the pre-treatments showed a tendency of protection. Moreover, all the animals exposed to Hg presented high Hg levels in the kidney, liver, and placenta when compared with control group. Pregnant rats pre-exposed to Zn (Zn-Hg and Zn/NAC-Hg groups) presented an increase in hepatic metallothionein levels. Therefore, lactating rats exposed to Hg presented renal and blood δ-ALA-D inhibition; the pre-treatments showed a tendency to prevent the renal δ-ALA-D inhibition and prevented the blood δ-ALA-D inhibition caused by Hg. Lactating rats exposed to Hg presented high Hg levels in the kidney and liver. These results showed that 10 mg/kg of HgCl₂ causes biochemistry alterations in pregnant and lactating rats, and Zn and NAC present promising results against these damages.

Relationship between heavy metal accumulation and histological alterations in voles from alpine and forest habitats of the West Carpathians

The interaction between toxic heavy metals and bio-elements in internal organs and femoral bones and their potential impacts on bone structural properties and renal histopathological changes in bank voles and snow voles were investigated. Our results reveal that heavy metals Hg and Pb accumulate more in femoral bones of alpine habitats than forests. In snow voles, the parameters of the primary osteons' vascular canals (length, average perimeter and area) simultaneously decreased with an increase of Pb and Sr. Wider primary osteons' vascular canals of snow voles contained decreased levels of K, but increased Ba. In bank voles, the number of primary osteons increased in alpine habitats along with K, Hg, and Pb accumulation. In the kidneys of bank voles, rising levels of Rb, Hg, and Zn were detected in alpine habitats. Hg increases the most in kidney tissue from alpine habitats in both vole species, and Hg levels (mean value 0.25 μg/g, max. value 0.55 μg/g) in the renal tissues of bank voles from alpine localities are similar to Hg levels from Hg-polluted industrial areas in other studies. This reflects that alpine areas of the Tatra Mountains are highly contaminated with Hg. The intensity of renal hemosiderosis relates significantly to Zn, Fe, and Cu levels in snow voles, with Fe and Zn levels in bank voles from forest habitats, and with Rb in bank voles from alpine habitats. The intensity of tubule necrosis in renal tissues of bank voles from alpine habitats was negatively related to Se content. In bank voles from forest habitats, significant positive correlations were found between the intensity of glomerular hyperplasia and amounts of Zn. The interactions of the detected element's association with bone tissue and internal organs are discussed.

Neurochemical dysfunction in motor cortex and hippocampus impairs the behavioral performance of rats chronically exposed to inorganic mercury

Chronic exposure to mercury chloride (HgCl₂) has been shown to promote oxidative stress and cell death in the central nervous system of adult rats displaying motor and cognitive impairments. However, there are no investigations about neurochemical function after this type of exposure in rodents that may be associated with those behavioral changes already reported. Thus, the aim of this study was to analyze glutamatergic and GABAergic dysfunctions in the motor cortex and hippocampus of adult rats, in a model of chronic exposure to HgCl₂ in. Twenty rats were exposed to a daily dose of 0.375 mg/kg for 45 days. After this period, they were submitted to motor and cognitive functions tests and euthanized to collect the motor cortex and hippocampus for measurement of mercury (Hg) levels in the parenchyma and neurochemical assays for analysis of glutamatergic and GABAergic functions. It was observed that chronic exposure to HgCl₂ promoted increase in total Hg levels in these two brain areas, with changes in glutamatergic transport, but without changes in GABAergic transport. Functionally this model of exposure caused the decrease of the spontaneous motor locomotion and in the process of learning and memory. In this way, our results provide evidences that glutamatergic neurochemical dysfunction can be pointed out as a strong causal factor of motor and cognitive deficits observed in rats exposed to this HgCl₂.

Copper attenuates early and late biochemical alterations induced by inorganic mercury in young rats

Mercury (Hg), a divalent metal, produces adverse effects predominantly in the renal and central nervous systems. The aim of this study was to determine the effectiveness of copper (Cu) in prevention of mercuric mercury (Hg²⁺)-mediated toxic effects as well as the role metallothioneins (MT) play in this protective mechanism in young rats. Wistar rats were treated subcutaneously with saline (Sal) or CuCl₂.2H₂O (Cu 2.6 mg/kg/day) from 3 to 7 days old and with saline or HgCl₂ (Hg 3.7 mg/kg/day) from 8 to 12 days old. The experimental groups were (1) Sal-Sal, (2) Cu-Sal, (3) Sal-Hg, and (4) Cu-Hg. MTs and metal contents were determined at 13 and 33 days of age. Porphobilinogen synthase (PBG-synthase) activity as well as renal and hepatic parameters were measured at 33 days. At 13 day, Hg²⁺ exposure increased hepatic MT, Hg, zinc (Zn) and iron (Fe) levels, in kidney elevated Cu and Hg and decreased renal Fe concentrations, accompanied by elevated blood Hg levels. At 33 days, Hg²⁺ exposure inhibited renal PBG-synthase activity, increased serum urea levels and lowered Fe and Mg levels. Copper partially prevented the rise in blood Hg and liver Fe noted at 13 days; and completely blocked urea rise and diminished renal PBG-synthase activity inhibition at 33 days. In 13-day-old rats, Cu exposure redistributed the Hg in the body, decreasing hepatic and blood levels while increasing renal levels, accompanied by elevated renal and hepatic MT levels in Hg²⁺-exposed animals. These results suggest that hepatic MT might bind to hepatic and blood Hg for transport to the kidney in order to be excreted.

ABBREVIATIONS

MT: metallothioneins; PBG-synthase: porphobilinogen synthase.

Exposure to Inorganic Mercury Causes Oxidative Stress, Cell Death, and Functional Deficits in the Motor Cortex

Mercury is a toxic metal that can be found in the environment in three different forms – elemental, organic and inorganic. Inorganic mercury has a lower liposolubility, which results in a lower organism absorption and reduced passage through the blood–brain barrier. For this reason, exposure models that use inorganic mercury in rats in order to evaluate its effects on the central nervous system are rare, especially in adult subjects. This study investigated if a chronic exposure to low doses of mercury chloride (HgCl2), an inorganic form of mercury, is capable of promoting motor alterations and neurodegenerative in the motor cortex of adult rats. Forty animals were exposed to a dose of 0.375 mg/kg/day, for 45 days. They were then submitted to motor evaluation and euthanized to collect the motor cortex. Measurement of mercury deposited in the brain parenchyma, evaluation of oxidative balance, quantification of cellular cytotoxicity and apoptosis and density of mature neurons and astrocytes of the motor cortex were performed. It was observed that chronic exposure to inorganic mercury caused a decrease in balance and fine motor coordination, formation of mercury deposits and oxidative stress verified by the increase of lipoperoxidation and nitrite concentration and a decrease of the total antioxidant capacity. In addition, we found that this model of exposure to inorganic mercury caused cell death by cytotoxicity and induction of apoptosis with a decreased number of neurons and astrocytes in the motor cortex. Our results provide evidence that exposure to inorganic mercury in low doses, even in spite of its poor ability to cross biological barriers, is still capable of inducing motor deficits, cell death by cytotoxicity and apoptosis, and oxidative stress in the motor cortex of adult rats.

Antioxidant and mercury chelating activity of Psidium guajava var. pomifera L. leaves hydroalcoholic extract

Mercury (Hg) is widely distributed in the environment and is known to produce several adverse effects in organisms. The aim of the present study was to examine the in vitro antioxidant activity and Hg chelating ability of the hydroalcoholic extract of Psidium guajava leaves (HEPG). In addition, the potential protective effects of HEPG against Hg(II) were evaluated using a yeast model (Saccharomyces cerevisiae). HEPG was found to exert significant antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenger and inhibition of lipid peroxidation induced by Fe(II) assays in a concentration-dependent manner. The extract also exhibited significant Hg(II) chelating activity. In yeast, Hg(II) induced a significant decrease in cell viability. In contrast, HEPG partially prevented the fall in cell viability induced by Hg(II). In conclusion, HEPG exhibited protective effects against Hg(II)-mediated toxicity, which may be related to both antioxidant and Hg(II)-chelating activities.

Chemical Speciation of Selenium and Mercury as Determinant of Their Neurotoxicity

The antagonism of mercury toxicity by selenium has been well documented. Mercury is a toxic metal, widespread in the environment. The main target organs (kidneys, lungs, or brain) of mercury vary depending on its chemical forms (inorganic or organic). Selenium is a semimetal essential to mammalian life as part of the amino acid selenocysteine, which is required to the synthesis of the selenoproteins. This chapter has the aim of disclosing the role of selenide or hydrogen selenide (Se^-2 or HSe^-) as central metabolite of selenium and as an important antidote of the electrophilic mercury forms (particularly, Hg²⁺ and MeHg). Emphasis will be centered on the neurotoxicity of electrophile forms of mercury and selenium. The controversial participation of electrophile mercury and selenium forms in the development of some neurodegenerative disease will be briefly presented. The potential pharmacological use of organoseleno compounds (Ebselen and diphenyl diselenide) in the treatment of mercury poisoning will be considered. The central role of thiol (-SH) and selenol (-SeH) groups as the generic targets of electrophile mercury forms and the need of new in silico tools to guide the future biological researches will be commented.

Zinc protection in fetal rats for maternal mercury exposure-induced growth retardation is probably associated with S100B expression

AIM

The study was conducted to investigate the effects of maternal mercury exposure on fetal rat development and zinc protection in mercury-exposed rats.

METHODS

Pregnant rats were subjected to zinc sulfate pre-feeding, mercury exposure and zinc sulfate co-feeding. The control rats were administered distilled water. On day 19, the placental weight, overall weight, size and tail length of fetal rats, mercury content and S100B level in the placenta were determined using Western blot analysis.

RESULTS

Compared with the control, mercury exposure at 2.0 mg/kg.d significantly reduced placental weight and fetal development, resulting in reduced fetal weight, size and tail length, while zinc pre-feeding increased placental weight and other fetal developmental parameters. Compared with mercury exposure, co-feeding with zinc significantly reduced mercury-induced injury in the fetal rats. S100B and mercury content levels were significantly elevated in rats maternally exposed to methylmercury chloride, compared with the unexposed control, while co-feeding with methylmercury chloride and zinc sulfate significantly reduced S100B and mercury levels in the placenta.

CONCLUSION

Maternal exposure to mercury results in increased S100B in the placenta. Zinc sulfate feeding could reduce S100B and mercury levels, thereby protecting the rats from mercury damage. S100B level may be used to measure the antagonism between zinc and mercury during pregnancy.

Effects of zinc against mercury toxicity in female rats 12 and 48 hours after HgCl2 exposure

This work investigated the toxicity of inorganic mercury and zinc preventive effects in female rats sacrificed 12 or 48 h after HgCl₂ exposure. Female Wistar rats were subcutaneously injected with ZnCl₂ (27 mg/kg) or saline (0.9 %), and 24 h later they were exposed to HgCl₂ (5 mg/kg) or saline (0.9 %). Rats sacrificed 12 hours after Hg administration presented an increase in kidney weight and a decrease in renal ascorbic acid levels. Zinc pretreatment prevented the renal weight increase. Rats sacrificed 48 h after Hg exposure presented a decrease in body weight gain, an increase in renal weight, a decrease in renal δ-aminolevulinic acid dehydratase activity, an increase in serum creatinine and urea levels, and a decrease in kidney total thiol levels. Zinc pretreatment partly prevented the decrease in body weight gain and increase in creatinine levels, in addition to totally preventing renal δ-aminolevulinic acid dehydratase inhibition. Mercury accumulation in the kidney and liver in both periods was observed after Hg administration. These results show the different Hg effects along the time of intoxication, and a considerably preventive effect of zinc against Hg toxicity.

Zinc and N-acetylcysteine modify mercury distribution and promote increase in hepatic metallothionein levels

This study investigated the ability of zinc (Zn) and N-acetylcysteine (NAC) in preventing the biochemical alterations caused by mercury (Hg) and the retention of this metal in different organs. Adult female rats received ZnCl2 (27mg/kg) and/or NAC (5mg/kg) or saline (0.9%) subcutaneously and after 24h they received HgCl2 (5mg/kg) or saline (0.9%). Twenty-four hours after, they were sacrificed and analyses were performed. Hg inhibited hepatic, renal, and blood δ-aminolevulinic acid dehydratase (δ-ALA-D) activity, decreased renal total thiol levels, as well as increased serum creatinine and urea levels and aspartate aminotransferase activity. HgCl2-exposed groups presented an important retention of Hg in all the tissues analyzed. All pre-treatments demonstrated tendency in preventing hepatic δ-ALA-D inhibition, whereas only ZnCl2 showed this effect on blood enzyme. Moreover, the combination of these compounds completely prevented liver and blood Hg retention. The exposure to Zn and Hg increased hepatic metallothionein levels. These results show that Zn and NAC presented promising effects against the toxicity caused by HgCl2.

Effectiveness of (PhSe)2 in protect against the HgCl2 toxicity

This work investigated the preventive effect of diphenyl diselenide [(PhSe)2] on renal and hepatic toxicity biomarkers and oxidative parameters in adult mice exposed to mercury chloride (HgCl2). Selenium (Se) and mercury (Hg) determination was also carried out. Mice received a daily oral dose of (PhSe)2 (5.0mg/kg/day) or canola oil for five consecutive days. During the following five days, the animals were treated with a daily subcutaneous dose of HgCl2 (5.0mg/kg/day) or saline (0.9%). Twenty-four hours after the last HgCl2 administration, the animals were sacrificed and biological material was obtained. Concerning toxicity biomarkers, Hg exposure inhibited blood δ-aminolevulinic acid dehydratase (δ-ALA-D), serum alanine aminotransferase (ALT) activity and also increased serum creatinine levels. (PhSe)2 partially prevented blood δ-ALA-D inhibition and totally prevented the serum creatinine increase. Regarding the oxidative parameters, Hg decreased kidney TBARS levels and increased kidney non-protein thiol levels, while (PhSe)2 pre-treatment partially protected the kidney thiol levels increase. Animals exposed to HgCl2 presented Hg content accumulation in blood, kidney and liver. The (PhSe)2 pre-treatment increased Hg accumulation in kidney and decreased in blood. These results show that (PhSe)2 can be efficient in protecting against these toxic effects presented by this Hg exposure model.

Distinct response of lactating and nonlactating rats exposed to inorganic mercury on hepatic δ-aminolevulinic acid dehydratase activity

This study investigated if lactating and nonlactating rats presented differences in relation to hepatic sensitivity to HgCl2 and the potential preventive role of ZnCl2. Lactating (days 3-12 of lactation) and nonlactating rats received 27 mg/kg ZnCl2 for five consecutive days and 5 mg/kg HgCl2 for five subsequent days. Lactating and nonlactating rats exposed to HgCl2 presented a decrease in food intake, a decrease in plasma alanine aminotransferase (ALT), and an increase in hepatic Hg levels when compared to the control group. Only lactating rats exposed to HgCl2 presented an increase in hepatic δ-aminolevulinic acid dehydratase activity. On the other hand, only nonlactating rats exposed to HgCl2 presented an increase in plasma aspartate aminotransferase (AST). ZnCl2 pre-exposure partially protected the increase in plasma AST activity presented by nonlactating rats and potentiated the liver Hg accumulation in lactating rats. Pups from the Sal-Hg and Zn-Hg groups showed a decrease in absolute liver weight and an increase in liver Hg levels. Summarizing, this study demonstrated that lactating rats presented distinct biochemical responses compared to nonlactating rats exposed to HgCl2 when hepatic parameters were evaluated.

Lactating and non-lactating rats differ in sensitivity to HgCl(2): Protective effect of ZnCl(2)

This work investigated zinc (Zn) and mercury (Hg) effects on oxidative parameters, markers of toxicity and metal levels in different tissues from non-lactating rats (NLR) and lactating rats (LR). Adult NLR and LR received ZnCl2 (27mg/kg) or saline (0.9%) subcutaneously and after 24h they received HgCl2 (5mg/kg) or saline (0.9%). Twenty four hours later, they were sacrificed and the preparation of biological material and biochemical analyses were performed. With respect to oxidative parameters, Hg exposure decreased kidney total SH levels from NLR and LR and hepatic catalase activity (not statistically significant) in NLR. Zinc pre-treatment partly prevented the decrease of kidney total SH levels in LR. Zinc per se increased hepatic non-protein SH levels of NLR and LR. Regarding toxicity markers, Hg exposure inhibited the δ-aminolevulinic acid dehydratase (δ-ALA-D) activity from kidney and liver of NLR, inhibited serum alanine aminotransferase (ALT) activity of LR and increased serum creatinine and urea levels of NLR and LR. Zinc pre-exposure prevented the enzymatic alterations caused by Hg. NLR and LR Hg exposed presented accumulation of mercury in the kidney, liver, blood and urine. Zinc pre-treatment prevented this accumulation partly in NLR liver and blood and completely in LR kidney and liver. These results show that NLR and LR are differently sensitive to HgCl2 and that ZnCl2 showed a promising effect against Hg toxicity.

The cytotoxicity of mercury chloride to the keratinocytes is associated with metallothionein expression

There are trace amounts of heavy metals in cosmetics. Heavy metals such as mercury (Hg), which is added to skin-whitening cosmetics, may cause acute or chronic damage to human cells. The aim of this study was to investigate the cytotoxicity of mercury chloride (HgCl₂) to human keratinocytes. The keratinocytes were treated with various concentrations of HgCl₂ and the cell survival fractions were found to be 38.08, 17.59, 12.76, 3.29 and 0.77% when the cells were treated with 0.25, 0.5, 0.75, 1 and 1.5 μM of HgCl₂, respectively. Moreover, we observed that the greatest damage was to the cell membrane. The metallothionein (MT) protein expression was also investigated. MT expression levels increased with increasing concentrations of HgCl₂. The results indicated that MT protects the keratinocytes against HgCl₂-induced toxicity.

Flow injection analysis of mercury using 4-(dimethylamino) benzaldehyde-4-ethylthiosemicarbazone as the ionophore of a coated wire electrode

A flow injection analysis (FIA) incorporating a thiosemicarbazone-based coated wire electrode (CWE) was developed method for the determination of mercury(II). A 0.1 M KNO(3) carrier stream with pH between 1 and 5 and flow rate of 1 mL·min(-1) were used as optimum parameters. A linear plot within the concentration range of 5 × 10(-6)–0.1 M Hg(II), slope of 27.8 ± 1 mV per decade and correlation coefficient (R2) of 0.984 were obtained. The system was successfully applied for the determination of mercury(II) in dental amalgam solutions and spiked environmental water samples. Highly reproducible measurements with relative standard deviation (RSD < 1% (n = 3)) were obtained, giving a typical throughput of 30 samples·h(-1).

High fiber probiotic fermented mare's milk reduces the toxic effects of mercury in rats

Background:

Since the advent of the Industrial Revolution in the late 19th century, we have all been unfortunately exposed to an increasingly toxic and polluted world. Among the most dangerous of these pollutants is mercury, which is considered to be the most toxic non-radioactive heavy metal. Fermented foods may help cleanse the body of heavy metals. Fermentation breaks down the nutrients in foods by the action of beneficial microorganisms and creates natural chelators that are available to bind toxins and remove them from the body.

Aims:

The current study was designed to determine the impact of feeding a high fiber probiotic fermented mare's milk on the biological effects of mercury toxicity in rat model.

Methods and Materials:

The high fiber fermented mare's milk containing probiotics was prepared and its sensory properties, chemical composition, and antioxidant activity were determined. A rat model of mercury toxicity was used. The effect of feeding the high fiber probiotic fermented mare's milk to rats, along with mercury ingestion, was determined by the analysis of several biochemical markers in serum and histopathological examinations of brain and kidney.

Results:

The high fiber fermented mare's milk containing probiotics was found to be acceptable by all test panels and volunteers. Mercury ingestion was found to cause biochemical and histopathological alterations in rat serum and tissues. The mercury-treated rats showed a decrease in body weight and an increase in kidney weight. Sera of the mercury treated rats showed alterations in biochemical parameters, and histopathological changes in brain and kidney. However, the rats fed high fiber fermented mare`s milk along with mercury ingestion showed improved histopathology of kidney and brain, and there was restoration of the biochemical parameters in serum to almost normal values.

Conclusions:

Feeding high fiber fermented mare`s milk may reduce the toxic effects of mercury.

Mercury chloride increases hepatic alanine aminotransferase and glucose 6-phosphatase activities in newborn rats in vivo

This work investigated the in vivo and in vitro effects of HgCl2 and ZnCl2 on metabolic enzymes from tissues of young rats to verify whether the physiological and biochemical alterations induced by mercury and prevented by zinc are related to hepatic and renal glucose metabolism. Wistar rats received (subcutaneous) saline or ZnCl2 (27 mg/kg/day) from 3 to 7 days old and saline or HgCl2 (5.0 mg/kg/day) from 8 to 12 days old. Mercury exposure increased the hepatic alanine aminotransferase (∼6-fold) and glucose 6-phosphatase (75%) activity; zinc pre-exposure prevented totally and partially these mercury alterations respectively. In vitro, HgCl2 inhibited the serum (22%, 10 μM) and liver (54%, 100 μM) alanine aminotransferase, serum (53%) and liver (64%) lactate dehydrogenase (10 μM), and liver (53%) and kidney (41%) glucose 6-phosphatase (100 μM) from 10- to 13-day-old rats. The results show that mercury induces distinct alterations in these enzymes when tested in vivo or in vitro as well as when different sources were used. The increase of both hepatic alanine aminotransferase and glucose 6-phosphatase activity suggests that the mercury-exposed rats have increased gluconeogenic activity in the liver. Zinc prevents the in vivo effects on metabolic changes induced by mercury.

Delayed biochemical changes induced by mercury intoxication are prevented by zinc pre-exposure

This work evaluated the delayed effects of mercury and the effectiveness of zinc in preventing such effects. Pups were pre-treated with 1 daily dose of ZnCl(2) (27 mg/kg/day, by subcutaneous injections) from 3rd to 7th postnatal day and received 1 daily dose of 5 mg/kg of HgCl(2), for 5 subsequent days (8-12 days old). Animals were euthanized 21 days after the end of Hg-exposure. Porphobilinogen-synthase activity as well as zinc and mercury contents was determined in the liver and kidneys. Alanine aminotransferase, aspartate aminotransferase and lactic dehydrogenase activities as well as urea, creatinine and glucose levels were analyzed in plasma or serum. Some animals were considered more sensitive to mercury, since they did not recover the body weight gain and presented an increase of renal and hepatic mercury content, urea and creatinine levels; a decrease in renal porphobilinogen-synthase and alanine aminotransferase activities, as well as a decrease in the liver and an increase in kidney weights. Some animals were considered less sensitive to mercury because they recovered the body weight and presented no biochemical alterations in spite of mercury in the tissues. Zinc prevents partially or totally the alterations caused by mercury even those that persisted for a long time after the end of exposure. These findings suggest that there is difference among the animals regarding the sensitivity to mercury.

Sensitivity of young rats to nicotine exposure: Physiological and biochemical parameters

This work has investigated the effects of prolonged exposure of young rats to nicotine on some physiological and biochemical parameters. Wistar male rats (30 days old) were treated (s.c.) with saline or nicotine 5mg/kg/day for 28 or 56 days. They received five injections (1mg/kg) per day (8, 10, 12:00 a.m., 2 and 4:00 p.m.) on the dark period of the cycle. Nicotine exposure for 56 days reduced body and liver weights. Moreover, nicotine exposure for 28 or 56 days decreased the hepatic glycogen but not blood glucose levels. The activities of blood and hepatic PBG-synthase, and blood and cerebral acetylcholinesterase were not affected by in vivo exposure. However, these activities were inhibited by nicotine in vitro. Results show that although high levels of plasma cotinine were found in both intervals of exposures, the parameters here analyzed were not affected by prolonged nicotine exposure except the storage of glucose, and body and liver weights.

Changes in levels of essential elements in suckling rats exposed to zinc and mercury

The effect of mercury and its interaction with zinc on the content of essential metals in tissues from neonate rats was investigated. Three-day-old Wistar rats were treated with saline or 27 mg kg(-1)d(-1) ZnCl2 (s.c.) for five consecutive days. From the 8th to the 12th day of life, the rats received one daily dose of saline or 5.0 mg kg(-1) HgCl2 (s.c). Twenty-four hours after the last injection liver, kidneys and blood were collected for metal quantification. The HgCl(2) exposure induced alterations on metal levels, such as increase of Fe, Hg and Zn in liver, decrease of Fe and Mg and increase of Cu and Hg contents in kidneys. The Hg exposure also increased Hg levels in the blood. The treatment with ZnCl2, administered previously to HgCl2, partially prevented the increase of Fe in the liver, and not only prevented the decrease of renal Mg but also increased it to levels higher than those found in control group. The Zn-Hg rats also presented higher renal Cu levels, and showed partially lower blood and hepatic Hg levels and higher renal Hg levels. The pre-administration of Zn caused no severe alterations in levels of essential metals (Cu, Fe, Mg and Mn). In short, Zn appears to be an alternative treatment of Hg poisoning in young animals in comparison to chelating drugs since these have low metal selectivity.