Article

Effect of Glutathione (GSH) Depletion on the Serum Levels of Triiodothyronine (T 3 ), Thyroxine (T 4 ), and T 3 /T 4 Ratio in Allyl Alcohol–Treated Male Rats and Possible Protection With Zinc

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Abstract

The current study is an attempt to elucidate the link between glutathione (GSH) as a major endogenous antioxidant and the thyroid hormone levels. Rats were treated with a single intraperitoneal (IP) dose of either ZnCl2 (5 mg/kg) or allyl alcohol (AIAI) (1.5 mmol/kg), which acts as a GSH-depleting agent. ZnCl2 and AIAI were administered either alone (Zn- and AlAl-treated groups) or in combination (AIAI + Zn-treated group). Blood and liver samples were collected 5 hours post treatment in all groups. Zinc was used because of its potential intracellular regulatory effect as a calcium antagonist. The data indicate a decrease in the serum levels of triiodothyronine (T3) and thyroxin (T4), the T3/T4 ratio, and serum and liver total protein in AlAl-treated rats. Increases in the serum levels of aminotransferases, hepatic calcium, and lipid peroxidation products were observed. The decrease in T3 and the T3/T4 ratio indicates a reduced capacity of the microsomes to convert T4 into T3. Rats treated with AlAl + Zn had replenished hepatic GSH and showed a marked decrease in the serum levels of aminotransferases and in the liver calcium contents and lipid peroxidation products compared to AlAl-treated rats. In contrast, zinc treatment failed to normalize the serum levels of total protein, T3 and T4, and the T3/T4 ratio in the same rats. Rat treated with ZnCI2 alone tended to have a lower serum protein level that was accompanied with a significant decrease in both serum T3 and the T3/T4 ratio. The effect of zinc in increasing capillary permeability with the probable leakage of some serum proteins including the thyroid-binding proteins could possibly be the reason behind this finding. Possible covalent binding of AIAI metabolites to some cellular proteins may explain the persistence of reduced liver protein levels in zinc-protected rats.

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... (Rudolf et al. 2001). Because of its ability as a free radical scavenger and a biological membrane stabilizer, numerous studies were designed to explore the protective role of Zn in many free radicals initiating systems (Hanna et al., 1993, Moustafa et al., 2000, Moustafa, 2001and Moustafa, 2003. Moreover, recent studies have reported the beneficial effect of antioxidants and zinc supplementation in restraining the progression to advanced age-related macular degeneration (Evans 2002), and 3 in the protection against cancer (Provinciali, et al., 2002). ...
... (c) Alloxan plus zinc chloride (ZnCl 2 )treated group which received a single. ip dose (100mg/kg) together with a single ip dose of ZnCl 2 (5 mg/kg ) ( Moustafa, 2001). Five rats were sacrificed with the same schedule as group b. ...
... The mechanism of Zn protection against oxidative damage may lie in its ability to bind and stabilize cellular and subcellular membranes against lipid peroxidation and disintegration (Thomas et al. 1986). Zn treatment was reported to reduce lipid peroxidation in the retinas and livers of alloxan-treated rats (Moustafa, 2003) and in the livers of allyl alcohol-treated rats (Moustafa, 2001). The protective effect of Zn against lipid peroxidation (of cellular and subcellular membranes) may reverse the impairment in glucose transport and glucose metabolism in the cells of alloxan-diabetic rats. ...
Article
In the present study male albino rats weighing 200 ± 50 g were made diabetic by injection with a single ip dose of alloxan (100 mg/kg). Another group of rats was simultaneously treated with alloxan (100 mg/kg) and a single ip dose of zinc chloride (ZnCl 2) (5 mg/kg). Blood and tissue samples were collected at 24, 48 and 72 hours post-treatment in both groups. Plasma insulin was significantly higher than control 24 hours after treatment in both alloxan and alloxan plus Zn treated groups, and then decreased 48 and 72 hours post treatment in both groups. The reduction was significant after 72 hours in alloxan treated group. A reduction in pancreatic glutathione (GSH) concentration was observed in alloxan-treated rats compared with control values at all sampling times of the experiment. When alloxan and ZnCl 2 were administered simultaneously, alloxan-induced reduction in pancreatic GSH was diminished, and a significant high GSH values were recorded relative to those recorded after treatment with alloxan alone 24, 48 and 72 hours post treatment. Alloxan has induced a significant increase in the serum levels of creatinine, urea and blood urea nitrogen (BUN), 24 hours after treatment, which returned nearly to their normal levels 48 and 72 hours after alloxan injection except for the levels of urea and blood urea nitrogen (BUN) which were dramatically declined 48 hours after treatment before its return to the control level 72 hours following alloxan intoxication. The concentrations of serum metabolites were unchanged due to the simultaneous treatment with alloxan and ZnCl 2 as compared to their concentrations in alloxan alone-treated rats except after 48 hours where alloxan plus Zn treatment has caused a significant elevation in the serum levels of urea and BUN relative to their values in alloxan alone-treated rats. A significant increase in liver glycogen level was observed 24 hours after alloxan and alloxan plus Zn treatments. Afterwards, it was markedly depleted by the two treatments 48 and 72 hours post treatment. The current results clearly indicate that the deleterious effects of alloxan were attenuated at many points by the simultaneous treatment with Zn. Of special importance was the effect of Zn in lowering the blood glucose concentration and replenishing the pancreatic GSH content.
... The animals were randomly segregated into four groups, viz. one normal control group (received saline), two zinc groups (Zn low : 4 mg/kg of zinc; Zn high : 8 mg/kg) (Bay et al., 1998;Moustafa, 2001), and a cyclophosphamide group (50 mg/kg of PC, as positive control of micronucleated polychromatic erythrocytes (MPCEs)). Saline or zinc acetate was administered intraperitoneally to the rats once every 2 days, seven times in total. ...
... When T3/T4 level increase, negative feedback shuts off TRH and TSH secretion. Moustafa observed a significant decrease in the levels of serum T3 and no change in the level of serum T4 in rats treated with ZnCl 2 (Moustafa, 2001). Our data also showed that the level of serum T3 was significantly decreased by zinc acetate, while there were no significant changes in the levels of serum T4 and TSH in the two zinc groups, compared with the normal control group (P > 0.05) showing that zinc indeed has a inhibitive effect on the function of thyroid hormone. ...
... Our data also showed that the level of serum T3 was significantly decreased by zinc acetate, while there were no significant changes in the levels of serum T4 and TSH in the two zinc groups, compared with the normal control group (P > 0.05) showing that zinc indeed has a inhibitive effect on the function of thyroid hormone. The decrease in serum T3 level may be associated with impaired thyroid conversion of T4 to T3 (Moustafa, 2001;Chaurasia et al., 1996). In addition, we also observed that the level of serum cortisol, another adrenal corticoid hormone in rats, was increased by zinc acetate in a dose-dependent manner. ...
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In order to expand our knowledge of zinc toxicity and to assess further the toxicities of zinc systematically, we observed the toxic effects of zinc on the functions of various tissues and organs in rats. The rats were randomly divided into four groups (14 in each group), viz. one normal control group (received saline), two zinc groups (Znlow: 4 mg/kg of zinc acetate; Znhigh: 8 mg/kg of zinc acetate), and one cyclophosphamide group (50 mg/kg, as positive control of micronucleated polychromatic erythrocytes (MPCEs)). Saline and zinc acetate were administered intraperitoneally to the rats once every 2 days, seven times in total. Cyclophosphamide was given intraperitoneally to the rats once. The concentration of blood zinc was determined and accumulation of zinc was not observed in the experimental groups. The frequencies of basophilic stippled erythrocyte (BSE) and MPCEs in the Znhigh group were significantly higher than those in the control group (P<0.05). The levels of serum glutamic oxalacetic transaminase (GOT) and serum triiodothyronine (T3) in the Znhigh groups decreased significantly, compared with the control group (P<0.01 or 0.05). Moreover, we also observed that the level of serum cortisol, another adrenal corticoid hormone in rats, was increased by zinc acetate in a dose-dependent manner. According to the literature and our findings, exposure to zinc, especially at higher doses, may produce toxic effects on various tissues and organs including the hematopoietic system, cytogenetics, biochemistry and endocrine system function. Therefore, it is suggested that zinc should be used carefully, especially by high risk groups such as children and pregnant women despite its use as a food additive or in self-medication. At the same time, it is necessary to investigate and research further these toxicities of zinc with long-term administration of low dosage.
... The experimental design is described in Table 1. Doses for range-finding studies were based on previously published literature (Ganter et al. 2005;Ippolito et al. 2016;National Toxicology Program 2010;Yu et al. 2002;Jaeschke, Kleinwaechter, and Wendel 1987;Moustafa 2001). Upon completion of the dosing phase, animals were humanely euthanized by isoflurane anesthesia followed by exsanguination. ...
... AA and 4,4'-MDA exposures were both associated with biliary hyperplasia and bridging portal fibrosis. AA metabolizes to acrolein by alcohol dehydrogenase in periportal hepatocytes, resulting in glutathione depletion and periportal fibrosis (Jaeschke, Kleinwaechter, and Wendel 1987;Moustafa 2001). Similarly, 4,4'-MDA converts to toxic metabolites in the periportal region of the liver, resulting in the portal damage observed in this study and other reports (Zhang et al. 2006). ...
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More than 80,000 chemicals are in commercial use worldwide. Hepatic metabolism to toxic intermediates is often a key mechanism leading to tissue damage and organ dysfunction. Effective treatment requires prompt detection of hepatotoxicity, ideally with rapid, minimally invasive diagnostic assays. In this study, archetypal histologic features of chemically induced hepatic injury were compared with clinical chemistries (including liver enzymes) and serum concentrations of microRNA-122 (miR-122, the processed form miR-122-5p), a biomarker of liver injury. The hepatotoxicants 4,4’-methylenedianiline (4,4’-MDA), allyl alcohol (AA), or carbon tetrachloride (CCl4) were orally administered to male Sprague-Dawley rats for 1, 5, 14, or 28 days to induce liver damage. Formalin-fixed, paraffin-embedded liver sections were evaluated histologically for inflammation, fibrosis, necrosis, and lipid accumulation. Liver enzymes were measured in serum, and serum miR-122 concentrations were assessed by quantitative polymerase chain reaction (qPCR). Histologic features of hepatic injury dose-dependently increased in both severity and frequency. Increases in liver enzymes and bilirubin were more pronounced in response to AA or 4,4’-MDA than to CCl4 at early time points. Elevated serum miR-122 levels in animals administered CCl4, AA, or 4,4’-MDA were more strongly associated with degree of hepatic histopathology than with dosage. Given this sensitive expression pattern postexposure, liver-specific miR-122 may improve the diagnostic accuracy of early hepatic injury.
... Nano-zinc oxide is a key element for the maintenance of the structural and functional integrity of eukaryotic cells and tissues [19]. Many studies have addressed the importance of ZnO as an antioxidant and a therapeutic agent in several free radicals initiating systems [20][21][22][23][24] and reported the antidiabetic effects of ZnONPs through induction of insulin, IR, and glucose metabolizing enzymes gene expression. In the same line Umrani and Paknikar, [25] proved the ability of ZnONPs for controlling blood glucose in diabetic rats, these are only two studies that monitored the effect of ZnONPs on diabetic rats, but there is not previous study carried out with F: ZnO and Cl:ZnO nanoparticles on diabetic rats. ...
... Nano-zinc oxide is a key element for maintenance of the structural and functional integrity of eukaryotic cells and tissues [19]. Many studies have addressed the importance of ZnO as an antioxidant and a therapeutic agent in several free radicals initiating systems [20][21][22][23][24] reported the antidiabetic effects of ZnONPs through induction of insulin, IR and glucose metabolizing enzymes gene expression. In the same line Umrani and Paknikar, [25] proved the ability of ZnONPs for controlling of blood glucose in diabetic rats, these are only two studies that monitored the effect of ZnONPs on diabetic rats, but there is not previous study carried out with F:ZnO and Cl:ZnO nanoparticles on diabetic rats. ...
Article
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Oxidative stress is a basic mechanism behind the development of diabetic retinopathy (DR). Therefore, the present study conducted to evaluate the protective effect of zinc oxide nanoparticles (ZnONPs) doped with fluorine (F:ZnO) and chlorine (Cl:ZnO), on retinal oxidative stress in type II diabetic rats. TEM showed that the F:ZnO and Cl:ZnO have average particle size 17.7 and 59.3 nm, respectively. The results indicated that serum glucose was increased significantly (p ≤ 0.05) and serum insulin was decreased significantly 3 days after treatment with STZ compared to other groups. STZ treatment depleted both retinal and liver TBA and retinal GST contents. While, simultaneous treatment rats with low and high dose of STZ + F:ZnO and STZ + Cl:ZnO were decreased serum glucose induced by STZ and reversed the deplete influence on GSH level of retinal and reduced the highs in TBA levels of livers and retinas in STZ -administrated rats. The results investigate the useful effects of high dose of F:ZnO and Cl:ZnO in protection diabetic rats against hyperglycemia and retina against oxidative stress.
... Moreover, Zinc status and serum thyroid hormone levels were improved in goitrous patients after six months treatment with Zinc supplementation [49]. On the other hand, suppression of T3 and T3/T4 was found in a study in which rats were supplemented with Zinc chloride, due to a reduction in microsomal capacity to convert T4 to T3 [50]. Our results are not consistent with these reports. ...
Article
The aim of the study was to investigate the effect of Iron, Zinc, Vitamin C (Vit.C) and Vitamin E (Vit.E) supplementation on thyroid hormones in rats with hypothyroidism. Thirty six rats were divided into two main groups, the first main group (6 rats) was fed on basal diet only. The second main group (30 rat) were injected with 10 mg/kg/day Propylthiouracil (PTU) to induce hypothyroidism, was divided into 5 subgroups: including control positive group that fed on basal diet, and the other subgroups were fed on basal diet supplemented with 40 mg ferric sulphate/kg diet, 200 mg zinc carbonate /kg diet, 250 mg α- tocohperol acetate/kg/B.W. and 250 mg ascorbic acid/kg/B.W. respectively. Blood samples were collected from each rat and were centrifuged to obtain serum. PTU exposed rats showed hypothyroidism with significant (P<0.05) decline in serum FT3 and FT4 levels together with significant (P<0.05) increase in serum TSH level. The supplementation with Iron, Zinc, Vit.E or Vit.C significantly (P<0.05) increased the level of thyroid hormones (FT4 and FT3) and glutathione peroxidase, moreover, the level of TSH was significantly (P<0.05) decreased, compared with control positive group, might be due to their antioxidant properties. Significant improvement in lipid profile as well as liver and kidney functions were observed. It could be suggested that Vitamin C, Vitamin E, Zinc and Iron could be used as a suitable supplementation therapy for hypothyroidism patients.
... In concordance with previous reports, allyl alcohol and 4,4'-methylenedianiline showed microscopic evidence of fibrosis within the five-day study interval (Ganter et al., 2005; National Toxicology Program, 2010). Allyl alcohol rapidly converts to acrolein in the periportal hepatocytes, resulting in rapid glutathione depletion and localization of fibrosis to the periportal region (Jaeschke et al., 1987; Moustafa et al., 2001). Previous reports concur with our data demonstrating that Tgfb1 mRNA expression increases with extent of fibrotic injury, with considerable inter-individual variability (Jung et al., 2000). ...
Article
TOXIC INDUSTRIAL CHEMICALS INDUCE LIVER INJURY, WHICH IS DIFFICULT TO DIAGNOSE WITHOUT INVASIVE PROCEDURES: Identifying indicators of end organ injury can complement exposure-based assays and improve predictive power. A multiplexed approach was used to experimentally evaluate a panel of 67 genes predicted to be associated with the fibrosis pathology by computationally mining DrugMatrix, a publicly available repository of gene microarray data. Five-day oral gavage studies in male Sprague-Dawley rats dosed with varying concentrations of three fibrogenic compounds (allyl alcohol, carbon tetrachloride, and 4,4'-methylenedianiline) and two non-fibrogenic compounds (bromobenzene and dexamethasone) were conducted. Fibrosis was definitively diagnosed by histopathology. The 67-plex gene panel accurately diagnosed fibrosis in both microarray and multiplexed-gene expression assays. Necrosis and inflammatory infiltration were comorbid with fibrosis. ANOVA with contrasts identified that 51 of the 67 predicted genes were significantly associated with the fibrosis phenotype, with 24 of these specific to fibrosis alone. The protein product of the gene most strongly correlated with the fibrosis phenotype (Pcolce) was dose-dependently elevated in plasma from animals administered fibrogenic chemicals (p<0.05). Semi-quantitative global mass spectrometry analysis of the plasma identified an additional 5 protein products of the gene panel which increased after fibrogenic toxicant administration: fibronectin, ceruloplasmin, vitronectin, insulin-like growth factor binding protein, and α2-macroglobulin. These results support the data mining approach for identifying gene and/or protein panels for assessing liver injury and may suggest bridging biomarkers for molecular mediators linked to histopathology.
... Our results are partially consistent with other reports where decrease in T 3 was recorded, while T 4 level was not significantly changed [40]. However, other studies are completely comparable to these findings where treatment of rats with CCl 4 and allyl alcohol significantly decreased T 3 and T 4 level [41,42]. ...
Article
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In the current study protective effect of ethanol extract of Pistacia chinensis bark (PCEB) was investigated in rats against CCl4 induced lung and thyroid injuries. PCEB dose dependently inhibited the rise of thiobarbituric acid-reactive substances, hydrogen peroxide, nitrite, and protein content and restored the levels of antioxidant enzymes, that is, catalase, peroxidase, superoxide dismutase, glutathione-S-transferase, glutathione reductase, glutathione peroxidase, γ-glutamyl transpeptidase, and quinone reductase in both lung and thyroid tissues of CCl4 treated rats. Decrease in number of leukocytes, neutrophils, and hemoglobin and T3 and T4 content as well as increase in monocytes, eosinophils, and lymphocytes count with CCl4 were restored to normal level with PCEB treatment. Histological study of CCl4 treated rats showed various lung injuries like rupture of alveolar walls and bronchioles, aggregation of fibroblasts, and disorganized Clara cells. Similarly, histology of CCl4 treated thyroid tissues displayed damaged thyroid follicles, hypertrophy, and colloidal depletion. However, PCEB exhibited protective behaviour for lungs and thyroid, with improved histological structure in a dose dependant manner. Presence of three known phenolic compounds, that is, rutin, tannin, and gallic acid, and three unknown compounds was verified in thin layer chromatographic assessment of PCEB. In conclusion, P. chinensis exhibited antioxidant activity by the presence of free radical quenching constituents.
... Zn is a key element for maintenance of the structural and functional integrity of eukaryotic cells and tissues [58]. Many studies have addressed the importance of Zn as an antioxidant and therapeutic agent in several free radical initiation systems596061. Some studies have reported the beneficial effects of antioxidants and Zn supplementation in preventing progression to advanced age-related macular degeneration, and people supplemented with antioxidants and Zn are less likely to lose visual acuity [62]. ...
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Zinc (Zn) is an important nutrient that is involved in various physiological metabolisms. Zn dyshomeostasis is often associated with various pathogeneses of chronic diseases, such as metabolic syndrome, diabetes, and related complications. Zn is present in ocular tissue in high concentrations, particularly in the retina and choroid. Zn deficiencies have been shown to affect ocular development, cataracts, age-related macular degeneration, and even diabetic retinopathy. However, the mechanism by which Zn deficiency increases the prevalence of diabetic retinopathy remains unclear. In addition, due to the negative effect of Zn deficiency on the eye, Zn supplementation should prevent diabetic retinopathy; however, limited available data do not always support this notion. Therefore, the goal of this paper was to summarize these pieces of available information regarding Zn prevention of diabetic retinopathy. Current theories and possible mechanisms underlying the role of Zn in the eye-related diseases are discussed. The possible factors that affect the preventive effect of Zn supplementation on diabetic retinopathy were also discussed.
... Our results are partially consistent with other reports where decrease in TT 3 was recorded, while TT 4 level was not significantly changed (Itoh et al., 1987;Goel et al., 1994). However, other studies are completely comparable to these findings where treatment of rats with CCl 4 and allyl alcohol significantly decreased TT 3 and TT 4 level (Itoh et al., 1989;Moustafa, 2001). Significant decrease in TT 3 level was also reported in patients with various hepatic disorders (Itoh et al., 1986;Kano et al., 1987). ...
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Protective effects of Digera muricata (DM) methanol extract (DME) were evaluated against the oxidative stress of carbon tetrachloride (CCl 4) in the thyroid of male Sprague-Dawley rats. Treatment of CCl 4 1 ml/kg bw (25% CCl 4 /olive oil i.p) once a week for 16 weeks significantly decreased the activities of catalase, peroxidase, superoxide dismutase, glutathione-S-transferase and glutathione peroxidase in the thyroid. Level of reduced glutathione was decreased, while lipid peroxidation (TBARS) was significantly increased with CCl 4 in the thyroid of rat. CCl 4 significantly enhanced the level of thyroidal DNA injuries and AgNORs count. Serum level of TT 3 and TT 4 was significantly decreased, while TSH level was increased with CCl 4 treatment. Pleiomorphic histopathological abnormalities in thyroid were caused by CCl 4 treatment. Co-treatment of DME (100 and 200 mg/kg bw) intragastrically once a week for 16 weeks suppressed the toxic effects of CCl 4 and level of thyroid hormones, the activities of oxidative enzymes, glutathione (GSH) and TBARS concentration. Histopathological injuries induced with CCl 4 were remarkably reduced with co-treatment of DME in a dose dependent fashion. These results suggest that the ameliorative effects of DME could be attributed to radical scavenging or antioxidant properties.
... In a classical in vitro experiment, LaBella et al [18] demonstrated that zinc, in a dose-dependent manner, is a potent TSH releaser in sliced bovine pituitary glands. Moreover, zinc deficiency was proposed as a suppressing factor on thyroid hormones, and zinc supplementation had the opposite effect in rats [7,8], although this hypothesis is not in agreement with other publications192021. Many studies have demonstrated that there is an interaction between thyroid hormones and zinc metabolism, but the interactive mechanism remains unclear [4]. ...
Article
It is known that zinc interacts with thyroid hormones, altering plasma thyroid-stimulating hormones (TSH), triiodothyronine (T3), and tetraiodothyronine (T4) in rats and humans. To investigate whether zinc affects thyrotropin-releasing hormone (TRH)–stimulated TSH, 5 healthy men were tested at 8:00 am after an overnight fast. Elemental zinc (37.5 mg, as heptahydrated zinc sulfate) was administered orally, and TRH (200 μg) was administered intravenously for 1 minute. Blood samples were collected from an antecubital vein at −30, 0, 30, 60, 90, 150, 210, 240, 270, and 300 minutes. Serum zinc remained constant throughout the control period. However, serum zinc was significantly elevated after oral zinc administration in the experimental group (P < .05). Plasma TSH levels increased after TRH injection in the control and in the experimental group, although not significantly when comparing both groups. Moreover, no significant areas under the curves and no correlation between serum zinc and plasma TSH levels were detected in both groups studied. This is the first study that showed the relationship between TRH-stimulated TSH secretion during oral zinc tolerance test in healthy men. These results suggest that a single oral dose of zinc did not change TSH secretion after TRH injection. Furthermore, acute increases in blood TRH and TSH did not alter serum zinc levels.
... 27 In Zn deficient GMPs and GFPs the levels of FT3 and FT4 were decreased, when compared with normal subjects, these results are consistent with other study. 13 It was reported in a study conducted on rats that Zn chloride application lowered T3 and the T3/T4 ratio and this inhibition was attributed to a decrease in the microsomal capacity to convert T4 to T3. 28 This finding suggested that Zn deficiency suppressed TSH and leads to a reduction in thyroid hormones (Table 4). Free triiodothyronine and FT4 need Zn in order to fulfill its biological activity, and Zn deficiency affects the metabolic activity of these hormones in a negative way. 9 It is also possible that changes in Zn, selenium and iodine in the thyroid gland may affect thyroid function depending on TSH which led to changes in hormone levels. ...
Article
Zinc (Zn) is an essential element involved in many basic biochemical reactions in thyroid. The aims of present study is to evaluate the Zn status in biological samples and thyroid hormones levels in 60 goitrous male (GMPs) and 72 female patients (GFPs), before and after 6 months treatment with Zn supplementation and compared with non-goitrous subjects of both genders (M=106, F=120) of age range 16-30 years. The biological samples were analyzed for Zn concentration using flame atomic absorption spectrophotometer, following their microwave assisted acid digestion. Quality control for the methodology was established with certified samples and with those obtained by conventional wet acid digestion method on the same CRMs and real samples. The results showed that the significantly lower mean values of Zn in serum, while high level urine samples of GMPs and GFPs were observed as compared to control subjects (p<0.005 and 0.007) respectively. The mean values of free triiodothyronine and thyroxin were found to be lower in goitrous patients of both genders than in the age matched healthy control (p<0.006 and 0.002) respectively, in contrast high mean values of thyroid stimulating hormone were detected in GMPs and GFPs (p<0.009). It was observed that Zn status and serum thyroid hormone levels were improved in goitrous patients after six months treatment with Zn supplementation.
... Suppression of T3 and T3/T4 was found in a study in which rats were supplemented with zinc chloride, due to a reduction in microsomal capacity to convert T4 to T3 (Moustafa, 2001). Similarly, an in vitro study reports that zinc inhibits the conversion of T4 to T3 in brown lipid tissue (Pavia et al., 1999). ...
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There is an interrelationship between zinc and thyroid hormones, but the mechanisms surrounding this topic are unclear. The aim of this study was to investigate the effect of a single venous dose of zinc on plasma thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free tetraiodothyronine (FT4) in 10 healthy individuals, 5 of each sex. All of these individuals were studied after 25 mg zinc was administered intravenously for 1 min, at 8:00 a.m., after a 12-h fast. Blood samples were collected at -30, 0, 3, 30, 60, 90 and 120 min. There were no changes in the plasma levels of TSH, FT3 and FT4 in both groups studied after zinc administration. This study suggests that zinc in pharmacological doses does not significantly affect the hypothalamic pituitary thyroid axis in healthy individuals. The aim of the present study was to study the plasma profile of TSH, FT3 and FT4 following a single venous dose of zinc in healthy individuals, since zinc is a metal that affects thyroid hormone functions at several levels.
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The traditional utilization of donkeys (Equus asinus) as dairy animals has recently attracted substantial scientific interest with regard to human nutrition. Donkey milk is well tolerated by infants with cows' milk allergy, useful in the treatment of human immune-related diseases, in the prevention of atherosclerosis, and in-vitro studies showed an anti-proliferative effect. Active 3-3'-5-triiodothyronine (T3) in colostrum and milk could play different physiological roles, systemic and paracrine, for both the mother and the suckling offspring. The aim was to evaluate whether thyroid hormones (TH) concentrations in milk and blood of lactating donkeys change with the advancing lactation and whether they can be affected by dietary supplementation with several trace elements, some of them directly involved with TH synthesis (I), metabolism (Se) and action (Zn). Sixteen lactating jennies were divided into two groups (CTL and TE). Mixed feed for TE was added with Zn, Fe, Cu, Mn, I, Se and Co. Every 2 weeks milk and blood samples were collected at 11·00. Total concentrations of T3 in milk (T3M) and T3 and T4 in plasma (T3P and T4P) were assayed using ELISA kits, validated for the donkey species. T3M was not correlated with TH concentrations in blood, did not change with the stage of lactation, and was significantly higher in TE (4·09 ± 0·07 ng/ml, mean ± SE) than in CTL group (3·89 ± 0·08 ng/ml). T4P (81·8 ± 5·2 ng/ml) and T3P (15·2 ± 1 ng/ml) significantly changed with time, but were not significantly affected by dietary treatment. T3P/T4P ratio was significantly lower in TE group. This study indicates that in donkey milk the concentration of T3, a human-like bioactive compound, can be affected by trace elements intake.
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Selenium (Se) has an essential role in thyroid hormone metabolism. It has the potential to play a major part in the outcome of iodine (I) deficiency The aim of the present study was to evaluate the Se and I status of biological samples (serum and urine) of 160 goitrous male (GMPs) and 195 female patients (GFPs). The supplemental effects of Se (200 microg/day) and I (100 - 125 microg/day) were evaluated after 6 months. For comparison purposes, non-goitrous subjects of both genders (n = 440) with same age group and socioeconomic status were also selected. Hydride generation atomic absorption spectrometry (HGAAS) was used to investigate the Se concentration in the biological samples, prior to microwave assisted acid digestion. Quality control for the methodology was established by comparing the results obtained with certified samples with those obtained by conventional wet acid digestion method on the same CRMs and real samples. The mean serum Se concentration was significantly lower, while urinary Se was higher in GMPs and GFPs as compared to control subjects (p < 0.005 and < 0.007, respectively). The levels of I, free tri-iodothyronine, and thyroxin were found in goitrous patients of both genders were low compared to age matched healthy controls (p < 0.015, < 0.006, and < 0.002, respectively). On the other hand, high levels of thyroid stimulating hormone were observed in GMPs and GFPs (p < 0.009). It was observed that Se in biological samples of hypothyroid patients can play an important role in determining the severity of the hypothyroidism associated with iodine deficiency. A wide-scale epidemiological study is recommended together with the examination of the potential preventive role of Se supplementation in endemic goiter regions.
Article
It is well documented that oxidative stress is a basic mechanism behind the development of diabetic retinopathy (DR). The current study was undertaken to elucidate the possible role of zinc as an antioxidant and a biological membrane stabilizer in the protection against (DR). Male Wistar rats weighing 250 +/- 50 g were made diabetic by injection with a single ip dose of alloxan (100 mg/kg). Another group of rats was simultaneously treated with alloxan (100 mg/kg) and a single ip dose of zinc chloride (ZnCl2) (5 mg/kg). Blood and tissue samples were collected at 24, 48, and 72 h post-treatment in both groups. Diabetic state was confirmed by the determination of plasma glucose levels (significantly elevated at any time of the experiment when compared with controls receiving vehicle). Plasma insulin was significantly increased 24 h after treatment in both alloxan and alloxan plus ZnCl2-treated groups, and then decreased markedly 48 and 72 h post treatment in both groups. Alloxan treatment depleted both retinal and liver glutathione contents. The decrease in retinal and liver GSH in alloxan-treated rats was accompanied with a sustained increase in their thiobarbituric acid (TBA) content. Simultaneous treatment of rats with alloxan and ZnCl2 blunted the sustained increment in plasma glucose induced by alloxan. The combined administration of alloxan and zinc reversed the depleting effect on retinal and hepatic GSH in alloxan-treated rats and reduced the elevations in TBA content of both retinas and livers. At variance with many other antioxidants the current results clearly indicate the beneficial effects of Zn in both controlling hyperglycemia and the protection of the retina against oxidative stress in diabetes which may help set a new direction toward the development of effective treatments of DR.
Article
In order to investigate the effects of Zn on Pb toxicities. Proportion of abnormal sperm, percentage of micronucleated polychromatic erythrocyte (MPCE), serum thyroid hormones (T(3), T(4)) and cortisol were measured. Rats received intraperitoneal injection of 25 mg/kg Pb acetate, 4 mg/kg Zn acetate, both Pb acetate and Zn acetate, or normal saline as controls, once every two days, 7 times in total. No significant differences in whole blood Pb were detected between groups received Pb alone or both Pb and Zn. On the contrary, the concentration of whole blood Zn in the group given Zn alone was significantly higher than that in the group that received both Pb and Zn. In the groups given Pb alone or both Pb and Zn, proportion of abnormal sperm, frequency of MPCE and serum cortisol were significantly higher than those in controls, whereas serum T(3) and T(4) were significantly lower than in controls. In the group given both Pb and Zn, T(4) was decreased most obviously among the four groups. While the proportion of abnormal sperm was less in the group given both Pb and Zn than in the group given Pb alone. These findings suggest that Zn coadministration might alleviate toxic effects of Pb on the male reproductive system, whereas it could enhance the toxicity on thyroid function. Zn did not affect the toxicities of Pb on cytogenetic systems as indicated by MPCE percentage, and on serum cortisol levels under the dose of the present study. Our results suggested the double-edged effects of Zn on Pb toxicities in different organs. Therefore, the effects of Zn on Pb toxicities should be evaluated systematically.
Article
The present study was conducted to investigate how pinealectomy and zinc deficiency separately or in combination affected thyroid hormones in rats. The study was carried out on 40 Sprague-Dawley male rats. The rats were equally allocated to four groups: Group 1 (control group), Group 2 (zinc-deficient group), Group 3 (pinealectomized group) and Group 4 (pinealectomized and zinc-deficient group). At the end of a 4-week study period, the rats were decapitated and blood samples were taken. The samples were examined in terms of plasma zinc, melatonin, free and total T3, T4, and TSH. It was found that free T3 and T4 levels in the pinealectomized group (Group 3) were higher than all others (p < 0.01) while free T3, T4, and TSH levels in the zinc-deficient group (Group 2) were lower than all others (p < 0.01). Free T3 and T4 levels in the pinealectomized zinc-deficient group (Group 4) were lower than those in Groups 1 and 3 and higher than those in Group 2 (p < 0.01). The findings obtained at the end of the study period show that pinealectomy has a stimulating and zinc deficiency has a suppressing effect on thyroid hormones and that the suppressing effect caused by zinc deficiency is partially balanced by pinealectomy.
Article
To investigate microsomal changes in acute liver injury we determined whether liver T 4 -5'-deiodinase activity was correlated with serum triiodothyronine (T 3 ), thyroxine (T 4 ), and the T 3 /T 4 ratio in 21 rats treated with carbon tetrachloride (CCl 4 ). The T 3 concentration (r = 0.84, p < 0.001) and the T 3 /T 4 ratio (r = 0.89, p < 0.001) which were decreased 3 to 6 h after treatment were correlated significantly with liver T 4 -5'-deiodinase activity. The serum alanine transferase (ALT) concentration increased linearly after treatment and was significantly correlated with the T 3 content (r = -0.79, p < 0.001), the T 3 /T 4 ratio (r = -0.69, p < 0.001), and liver T 4 -5'-deiodinase activity (r = -0.69, p < 0.001). These results have not been reported and suggest that the decrease in T 3 concentration and the T 3 /T 4 ratio indicates a hepatic microsomal dysfunction in CCl 4 -treated rats, representing a significant inhibition of T 4 -5'-deiodinase activity.
Article
The possible mechanisms of ginseng saponins on the inhibition of the development of morphine tolerance and physical dependence were investigated in the aspects of morphine metabolism by morphine 6-dehydrogenase. The administrafion of morphine causes a reduction of non-protein sulfhydryl contents in the liver, because morphinone metabolized from morphine by morphine 6-dehydrogenase conjugates with sulfhydryl compounds. However, ginseng saponins inhibited the activity of morphine 6-dehydrogenase which catalyzed the production of morphinone from morphine. In addition, ginseng saponins inhibited the reduction of non-protein sulfhydryl levels by increasing the level of hepatic glutathione. These results suggest that the dual action of the above plays an important role in the inhibition of the development of morphine tolerance and physical dependence. On the other hand, it was observed that less polar components of ginseng saponins with parent structures were more active components in vitro.
Article
Intraperitoneal injection of the glutathione depleting agent, allyl alcohol (AIA1) (1.5 mmol/kg) into rats was found to induce a deterioration in glucose tolerance 4 hr posttreatment, which was accompanied by a reduced elevation in serum insulin levels in response to the glucose challenge. AIA1 produced a significant and progressive depletion in liver glycogen, while a significant increase in plasma lactate, pyruvate, creatinine, urea and blood urea nitrogen (BUN) was observed following A1A1 treatment. Elevated lactate and pyruvate levels were sustained for several hours after A1A1 intoxication. It is suggested that A1A1-induced lipid peroxidation may lead to an alteration in the rates of glucose transport and metabolism, which could be the reason behind the observed glucose intolerance in the treated rats. The current data present evidence that the primary energy-forming pathway is promptly impaired by glutathione depletion, which emphasizes the importance of glutathione in the maintenance of the redox potential of the cell. Perturbations in the redox state of the cell could alter many important functions of the cell including the cellular capacity to synthesize insulin and/or one or more of the glucose metabolizing enzymes.
Article
The serum tri-iodothyonine (T3), thyroxine (T4) and the T3/T4 ratio correlate significantly with the activities of liver microsomal enzymes such as carboxylesterase and T4-5-deiodinase in rats treated with carbon tetrachloride (CCl4). Treatment of rats with ginseng may alleviate liver lesions caused by CCl4. Current data indicate a decrease in T3 levels 24 h post-CCl4 treatment; a decrease in liver lipid concentrations with a concomitant increase in their plasma levels; an increase in both serum total proteins and γ-glutamyl transpeptidase activity; and the inhibition of both a rise in liver calcium and serum glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase in rats pretreated with ginseng compared with those treated with CCl4 alone. Serum T3 and T4 levels decrease significantly 6 and 24 h after CCl4 administration. An increase in the T3/T4 ratio was observed in the ginseng + CCl4-treated group compared with the CCl4-treated group, 6 and 24 h post-CCl4 administration, but it was not significant.
Article
Oxygen radicals have been implicated in a host of commonly occurring diseases, which possess an inflammatory component—including rheumatoid arthritis (RA), atherosclerosis, pulmonary emphysema, cancer, inflammatory bowel disease, and periodontal disease. Radicals are also implicated in the normal course of ageing. A wide variety of oxidized biomolecules—known to be specific products of free radical reactions—have been detected in extracellular fluids from patients with these inflammatory conditions. This chapter focuses on some of the mechanisms through which free radicals could be involved in pathogenesis, where the radicals themselves acts as both mediators and modulators of inflammatory reactions. In biological systems, oxygen is reduced to reactive oxygen intermediates (ROI) by a wide variety of both enzymic and non-enzymic pathways, as a result of normal metabolic processes. It is also assumed that in acute or chronic inflammation, one pathogenetic factor might be the disruption of normal metabolic balance between the production and removal of oxygen radicals, leading to cell damage. The chapter discusses some of the pathways by which oxidants may be produced.
Chapter
Tissue necrosis has long been known to be associated with the accumulation of large amounts of calcium in the necrotic tissue, and it has been proposed that the calcium ion may play a critical role in the development of lethal alterations of cell structure and function (Campbell, 1983). Although the generality of this hypothesis has been questioned (Starkeet al., 1986), the involvement of Ca2+ in the development of lethal cell injury is now supported by a large number of observations. For example, Shanne and associates (1979) found that removal of extracellular Ca2+ exerted a protective effect against the toxicity of a number of agents in cultured hepatocytes. This and similar observations led to the proposal that an influx of extracellular Ca2+ could play a predominant role in the development of irreversible cell damage (Chienet al., 1979; Farber, 1981). However, subsequent studies showed that an influx of extracellular Ca2+ is not necessarily required for cytotoxicity and that a disruption of intracellular Ca2+ homeostasis may also result in irreversible cell damage.
Article
The effects of all-zinc metallothionein (Zn-metallothionein) and predominantly cadmium metallothionein (Cd/Zn-metallothionein) on free radical lipid peroxidation have been investigated, using erythrocyte ghosts as the test system. When treated with xanthine and xanthine oxidase, Zn-metallothionein and Cd/Zn-metallothionein underwent thiolate group oxidation and metal ion release that was catalase-inhibitable, but superoxide dismutase-non-inhibitable. Similar treatment in the presence of ghosts and added Fe(III) resulted in metallothioneen oxidation that was significantly inhibited by superoxide dismutase. Ghosts incubated with xanthine/xanthine oxidase/Fe(III) underwent H2O2- and O2−-dependent lipid peroxidation, as measured by thiobarbituric acid reactivity. Neither type of metallothionein had any effect on xanthine oxidase activity, but both strongly inhibited lipid peroxidation when added to the membranes concurrently with xanthine/xanthine oxidase/iron. This inhibition was far greater and more sustained than that caused by dithiothreitol at a concentration equivalent to that of metallothionein thiolate. Significant protection was also afforded when ghosts plus Cd/Zn-metallothionein or Zn/metallothionein were preincubated with H2O2 and Fe(III), and then subjected to vigorous peroxidation by the addition of xanthine and xanthine oxidase. These results could be mimicked by using Cd(II) or Zn(II) alone. Previous studies suggested that Zn(II) inhibits xanthine/xanthine oxidase/iron-driven lipid peroxidation in ghosts by interfering with iron binding and redox cycling. Therefore, the primary determinant of metallothionein proteciion appears to be metal release and subsequent uptake by the membranes. These results have important implications concerning the antioxidant role of metallothionein, a protein known to be induced by various prooxidant conditions.
Article
Exposure of semiconfluent cultures of Madin-Darby canine kidney cells to 10 μm zinc leads to a change in the organization of the actin filament system. Most of the stress fibers at the basal end of the cell are lost and the actin associated with the lateral membrane and junctional regions appears to retract into the cytoplasm. In addition, at the base of the cell in regions of cell-substratum contact, dense, actin-rich plaques appear. These alterations in actin filaments are associated with a change in cell shape. Microtubules were unaffected by exposure to 10 μm zinc. At zinc concentrations ≥50 μm the microtubules depolymerized. Exposure to cadmium alters the actin filaments as well but the effect is different from the change seen with zinc. When the cells are exposed simultaneously to zinc and cadmium the cells appear the same as they would if exposed to zinc alone. Exposure of MDCK cells to either metal, individually or in combination, results in a significant and similar increase in F-actin content as determined spectrofluorometrically. The changes in organization and amount of F-actin are associated with a reduction in the ability of the cells to remain attached to the substrate, a toxic effect of these metals with regard to epithelial function. The results indicate that zinc, an essential metal, and cadmium, a highly toxic metal, interact with the actin cytoskeleton in intact cells.
Article
Male NMRI mice were fed a sucrose diet for 48 hr in order to reduce the hepatic glutathione content and to level off its diurnal variation. After administration of allyl alcohol (AA: 1.1 mmol/kg), hepatic glutathione (24.3 ± 7.0 nmol GSH/mg protein) was almost totally lost within the first 15min (<0.5 nmol GSH/mg protein). Subsequently, a massive lipid perioxidation was observed, i.e. the animals exhaled 414 ± 186 nmol ethane/kg/hr compared to 0.9 ± 0.8 of controls, and the hepatic TBA- reactive compounds had increased from 55 ± 16 pmol/mg protein in controls to 317 ± 163 after 1 hr. Concomitantly, a 40–45% loss of the polyunsaturated fatty acids (arachidonic and docosahexaenoic acid) in the liver lipids was observed. About 80% of the cytosolic alcohol dehydrogenase activity and about 50% of the microsomal P450-content were destroyed.
Article
A thiobarbituric acid (TBA) test procedure with reasonable reproducibility applicable to the assay of lipoperoxides in various animal tissue homogenates is described. It was concluded that the deproteinization of homogenate prior to coloration is not needed, but double wavelength measurement is necessary to avoid interference and the reaction should be performed with phosphoric acid at a definite pH near 2.0. The most reproducible procedure is as follows: To 0.5 ml of 10% homogenate of the tissue sample, add 3 ml of 1% H3PO4 and 1 ml of 0.6% TBA aqueous solution; stir and heat the mixture on a boiling water bath for 45 min. After cooling, add 4 ml of n-butanol, shake, and separate the butanol layer by centrifugation; determine the optical density of the butanol layer at 535 and 520 nm; and calculate the difference of optical density between the two determinations to be taken as the TBA value.
Article
The role of liver in the peripheral conversion of thyroxine (T4) to triiodothyronine (T3) was studied in normal subjects and patients with alcoholic liver disease by measurement of thyrotrophin (TSH) and total and free T4 and T3 in randomand serial serum samples. Also, T4 to T3 conversion rates and T3 disposal rates were compared by noncompartmental analysis. While the mean total serum T4 values were similar for the two groups, 8.6 and 8.1 mug/kl, the mean free T4 value was significantly higher in the cirrhotic patients (3.3 ng/dl) than in the normal subjects (2.1 ng/dl, P less than 0.001). The mean serum T3 value, 85 ng/dl, was significantly reduced in the hepatic patients as compared to a mean serum T3 value of 126 ng/dl in the normal subjects (P less than 0.001), while the free T3 value was 0.28 ng/dl in both groups. The reduction of the serum total and free T3 values were closely correlated with the degree of liver damage, as indicated by elevation of serum bilirubin (r equal -0.547) and reduction of serum albumin (r equal 0.471). The mean serum TSH level was 3.1 muU/ml in the normals and 7.1 muU/ml in the cirrhotic aptients ( less than 0.001). 15% of the hepatic patients had serum TSH values above 10 muU/ml, which, however, did not correlate with any of the four liver function tests studied. Serial blood sampling from two convalescing patients with alcoholic hepatitis showed a gradual normalization of serum TSH and T3 levels as the liver function improved. After oral T4 administration, 0.25 mg/day for 10 days, three of four cirrhotic patients studied failed to raise their serum T3 values. The mean T4 to T3 conversion rate of seven normal subjects was 35.7%. The mean T4 to T3 conversion rate of four cirrhotic patients studied was significantly reduced to 15.6% (P less than 0.001). The mean disposal rates of T4 and T3 of the normal subjects were 114 and 34 mug/day, respectively. The ratio of T4 disposal to T3 disposal was 3.5. In contrast, the mean T4 disposal rate, 82 mug/day, and the mean T3 disposal rate, 10 mug/day, were both reduced in the cirrhotic patients. Their ratio of T4 disposal to T3 disposal was 7.9. These findings suggest that impairment of T4 conversion in patients with advanced hepatic cirrhosis may lead to reduced T3 production and lowered serum T3 level. Therefore, the liver is one of the major sites of T4 conversion to T3.
Article
The calcium ionophore, A23187, can induce rat hepatic metallothionein (MT) when administered in vivo (5.8-fold, 5.0 microM, 11 h) and rat hepatocyte MT when administered in vitro (10.70-fold, 1.0 microM, 24 h). Several rat hepatoma cell lines (2M, 4.55-fold; JM2, 12.29-fold; EC3, 14.12-fold; HTC, 7.99-fold) and a normal rat liver cell line (Clone 9, 39.67-fold) were tested for their inducibility of MT mRNA by Cd2+ (10 microM, 8 h). Quantitatively, JM2 and 2M made the most MT mRNA, while HTC made the least. A23187 (0.1-7.0 microM) was studied as an inducer of MT mRNA in these cell lines (except for HTC) and in HeLa. A variety of responses and tolerances were seen with inductions ranging up to 32.11-fold. Quantitatively, the best responding cell lines were EC3 and 2M. A combination induction experiment, using TPA, a protein kinase C activator, and A23187 in EC3 cells revealed an additive effect of the two inducers on MT mRNA levels: TPA (10 nM), 11.71-fold; A23187 (3.0 microM), 6.71-fold; and TPA + A23187, 20.00-fold. These studies have implicated perturbations in cytosolic calcium ion concentrations, caused by the ionophore A23187, as being involved in the complicated signaling systems which can lead to induction of MT mRNA and protein.
Article
We studied the histochemistry of Ca in livers treated with CCl4, diltiazem (one of the Ca antagonists), and both agents together to determine whether hepatocytes or other parts of the liver lesions show Ca staining and whether the grade or location of Ca in these injuries varies. For Ca staining, cryostat sections were treated by the glyoxal-bis-(2-hydroxyanil) (GBHA)-method using O.C.T. imbedding compound instead of paraffin. Diltiazem-treated rats showed Ca granules in the bile canaliculi around the terminal hepatic veins and Kupffer cells 6 h after intragastric injection. Rats treated with CCl4 showed fine red granules in the cytoplasm of the hepatocytes around the terminal hepatic veins as soon as 5 min mildly and 2 h moderately after intraperitoneal injection. Hepatocytes around the terminal hepatic veins showed positive Ca granules 6 to 30 h after intragastric injection of CCl4. Hepatocytes stained by Ca showed acidophilic degeneration and coagulative necrosis. The hepatocytes of rats treated with both diltiazem and CCl4 revealed fewer Ca granules than those treated with CCl4 alone. In summary, Ca was stained by the GBHA method from the early stage of liver injury by CCl4 and was closely involved in acidophilic degeneration and coagulative necrosis of hepatocytes. The Ca staining in liver cells in CCl4-treated rats was decreased by diltiazem.
Article
The mechanisms of the liver damage produced by three glutathione (GSH) depleting agents, bromobenzene, allyl alcohol and diethylmaleate, was investigated. The change in the antioxidant systems represented by alpha-tocopherol (vitamin E) and ascorbic acid were studied under conditions of severe GSH depletion. With each toxin liver necrosis was accompanied by lipid peroxidation that developed only after severe depletion of GSH. The hepatic level of vitamin E was decreased whenever extensive lipid peroxidation developed. In the case of bromobenzene intoxication, vitamin E decreased before the onset of lipid peroxidation. Changes in levels of the ascorbic and dehydroascorbic acid indicated a redox cycling of vitamin C with the oxidative stress induced by all the three agents. Such a change of the redox state of vitamin C (increase of the oxidized over the reduced form) may be an index of oxidative stress preceding lipid peroxidation in the case of bromobenzene. In the other cases, such a change is likely to be a consequence of lipid peroxidation. Experiments carried out with vitamin E deficient or supplemented diets indicated that the pathological phenomena occurring as a consequence of GSH depletion depend on hepatic levels of vitamin E. In vitamin E deficient animals, lipid peroxidation and liver necrosis appeared earlier than in animals fed the control diet. Animals fed a vitamin E supplemented diet had an hepatic vitamin E level double that obtained with a commercial pellet diet. In such animals, bromobenzene and allyl alcohol had only limited toxicity and diethylmaleate none in spite of comparable hepatic GSH depletion. Thus, vitamin E may largely modulate the expression of the toxicity by GSH depleting agents.
Liver cytochrome P-450, b5, and serum thyroid hormones were measured before and 2-6 h after intra-peritoneal injections of CCl4 (1 mg/kg) in rats, to elucidate the relationship between serum thyroid hormones and liver microsomal function. Serum total protein, thyroxine (T4), free T4, triiodothyronine (T3), and cytochrome P-450 and b5 were decreased significantly after CCl4 administration, whereas reverse T3 (rT3) was unchanged. In addition to decreased conversion of T4 to T3 in liver microsomes, decreased serum binding capacities appeared to contribute to the change in serum hormone levels, since serum T4 correlated significantly with serum total protein. Serum T3, the T3/T3 + rT3 ratio, and the rT3/T3 ratio correlated significantly with cytochrome P-450 or b5, whereas the T3/T4 and T3/free T4 ratios did not. These results suggest that serum T3, the T3/T3 + rT3 ratio, and the rT3/T3 ratio are closely correlated with microsomal dysfunction in the severe case of CCl4-induced liver injury where serum binding proteins of thyroid hormones are decreased.
To study the relationship between the changes in hepatocytes and calcium contents in the liver of 42 rats treated with CCl4 and the effect of a calcium antagonist diltiazem on the liver injury, we determined liver calcium content, serum alanine aminotransferase (ALT), and serum levels of triiodothyronine (T3), thyroxine (T4), the T3/T4 ratio, and calcium before and 6 to 72 hr after treatment with a single oral dose of CCl4 (0.5 ml/kg) in 21 rats (Group I) and in 21 rats treated with diltiazem (10 mg/kg) intraperitoneally three times, 24 hr before, simultaneously with, and 24 hr after administration of the same doses of CCl4 (Group II). The maximum calcium content in Group I was 259.7 +/- 53.3 micrograms/g wet weight at 24 hr after treatment, whereas it was 113.0 +/- 51.1 micrograms/g wet weight in Group II, and a significant difference was seen between them (p less than 0.05). The ALT levels in both groups elevated after 18 to 24 hr and a significant difference was also found between the two levels at 24 hr (p less than 0.05). The T3/T4 ratio in Group I decreased immediately, but increased later. The ratio in Group II maintained the level before treatment. Correlation between the calcium content and the grade of centrilobular necrosis was significantly seen in Group I (r = 0.82, p less than 0.001), but was not found in Group II. The grade of centrilobular necrosis appeared to be more severe at 24 to 48 hr in Group I than in Group II.(ABSTRACT TRUNCATED AT 250 WORDS)
To evaluate the relation between liver calcium content and microsomal function in liver injury, we determined liver calcium content, serum triiodothyronine (T3), thyroxine (T4), T3/T4 ratio and serum glutamic pyruvic transaminase (SGPT) content in rats treated with CCl4. The T3/T4 ratio decreased from 1.9 to 1.2 at 6 hr after treatment, but elevated immediately to 3.2 at 36 hr after, and returned to normal at 54 hr after treatment. The calcium content increased from 27 micrograms/g wet weight to 448 micrograms/g wet weight 24 hr after treatment and decreased to normal 78 hr after treatment. The SGPT concentration showed the highest 12 hr after and returned to normal 72 hr after treatment. The calcium content was significantly correlated with T3 (r = -0.5, p less than 0.05). These results suggest that the increase and decrease in liver calcium content are closely related to the decrease and increase in T3 and T3/T4 ratio, respectively.
Article
The authors outline the progression of thought on the mechanism of the aging process, giving emphasis to environmental factors that influence genetic events. Discussion is limited to those theories that explain fundamental causes of aging and have a firm thermodynamic basis. The authors propose that the cumulative result of continual oxidative stress and other thermodynamic processes (such as amino-acid racemization and nonenzymatic glycosylation), resulting in altered function and increasing the net entropy of living systems, governs the rate of the aging process.
Article
This laboratory has previously postulated that bromobenzene-induced hepatic necrosis results from the formation of a reactive metabolite that arylates vital cellular macromolecules. Accordingly, the severity of liver necrosis has been compared with the formation of metabolites of bromobenzene and with covalent binding of metabolites in vivo and in vitro after various pretreatment regimens that alter hepatotoxicity. These data provide direct kinetic evidence that 3,4-bromobenzene oxide is the reactive hepatotoxic metabolite. The studies also demonstrate that the hepatotoxic metabolite is preferentially conjugated (detoxified) with glutathione, thereby depleting glutathione from the liver. Liver necrosis and arylation of cellular macromolecules occur only when glutathione is no longer available. Thus, a dose threshold exists for bromobenzene-induced hepatic necrosis.
Article
Our previous findings [Hazelton & Lang (1978) Fed. Proc. Fed. Am. Soc. Exp. Biol. 37(6), 2378 (abstr.)] demonstrated a senescence-specific decrease in glutathione (GSH) concentration in the yellow-fever mosquito Aedes aegypti (Louisville)]. As a possible mechanism for this change, GSH biosynthesis was investigated in adult mosquitoes of different ages through the life-span. Biosynthesis was measured as the incorporation rate of [14C]glycine or [14C]cystine into glutathione. Essential information to validate the procedure was also obtained on the precursor-amino-acid pool sizes and kinetic parameters such as lag-time and time course of incorporation. Also, synthesis de novo rather than exchange was verified using buthionine sulphoximine, a specific inhibitor of GSH biosynthesis. The synthetic rates with either amino acid precursor varied throughout the adult life-span, but the patterns for both precursors were essentially identical. Biosynthesis was high in the newly emerged adult and decreased 62-70% (P less than 0.005) to a plateau during maturity. From the mature value there was a decrease of 36-41% (P less than 0.005) to a new plateau during senescence. Glutathione biosynthesis and concentration were correlated throughout maturity and senescence (r = 0.982) and thus biosynthesis was proportional to glutathione content. On this basis we concluded that impaired biosynthesis is the major and perhaps sole mechanism for the aging decrease in glutathione content.
Article
The objective of this study was to explore the mechanism by which metabolic rate may affect life span by determining the relationship between lipid peroxidation potential and experimentally altered life spans in the adult housefly. Lipid peroxidation potential, measured in vitro, provides an indication of the relative conditions within the tissues affecting the susceptibility of polyunsaturated fatty acids to undergo non-enzymic peroxidation. Lipid peroxidation potential increased with age at a significantly faster rate in houseflies raised at 30 degrees C as compared to those kept at 25 degrees C. The life span of flies at 25 degrees C was longer and metabolic rate lower than at 30 degrees C. The effect of physical activity on lipid peroxidation potential was studied by comparing flies maintained under high and low physical activity regimes. Lipid peroxidation potential increased at a relatively greater rate with age in high-activity flies. The results suggest that accelerated senescence associated with higher metabolic rates, increases the rate of age-associated decline in the ability of houseflies to counteract lipid peroxidation in vitro.
Twenty-four hr after the subcutaneous injection of 0.015 mmol of mercuric chloride/kg/day into male rats for 2 days, the rats exhibited biochemical alterations in the kidneys, including diene conjugation absorption in the microsomal lipids, increased malonic dialdehyde content, decreased soluble glutathione (GSH) peroxidase activity. Simultaneous injections of 0.025 mmol of sodium selenite/kg/day restored the malonic dialdehyde content and the GSH peroxidase activity to normal levels. Incubation of kidney microsomes with low concentrations of mercuric chloride resulted in increased formation of lipid peroxides in the presence and the absence of ascorbate, but not in the presence of NADPH.
1. Heavy metals (Hg2+, Cu2+, Cd2+, Zn2+, Pb2+) at micromolar concentrations strongly inhibit the Ca(2+)-ATPase activity present in the plasma-membrane obtained from the gill cells of Mytilus galloprovincialis Lam. Heavy metals act through inhibition of the formation of the phosphorylated intermediate. 2. All the heavy metals tested inhibit the Ca(2+)-ATPase activity, the effect following the order: Hg2+ > Pb2+ > Cu2+ > Cd2+ > Zn2+; the simultaneous addition of different heavy metals causes a summatory inhibition of the enzyme activity; addition to the reaction mixture of GSH at a final concentration of 0.5 mM, reverses inhibitory effects of heavy metals. 3. The inhibitory effects of Cu2+ on Ca(2+)-ATPase are highly enhanced by addition of ascorbate to the reaction mixture. In the presence of ascorbate (100 microM), copper strongly stimulates the lipid peroxidation damage of the gill plasma-membranes, a result that may explain the high copper cytotoxicity.
Article
The .CCl3 radical generated during the metabolism of CCl4 is readily spin trapped in vivo and in vitro by phenyl N-tert-butylnitrone (PBN) to form the stable PBN/.CCl3 radical adduct, which can then be extracted into organic solvents and detected by ESR spectroscopy. We have used this technique to examine the proposed protective roles of Zn(II), Cr(III), and metallothionein (MT) against carbon tetrachloride toxicity in vivo. Hepatic MT, which is induced by Zn(II), has been proposed to protect against CCl4-induced cellular damage by scavenging the free radical metabolites formed. CCl4-induced hepatotoxicity was significantly suppressed in male Sprague-Dawley rats pretreated with a single dose of 5 mg/kg Zn(II) or Cr(III) according to standard serum assays for liver-specific enzymes, and hepatic MT was elevated after pretreatment with either Zn(II) or Cr(III). In vitro, no difference was detected in either the amount of CCl4-derived free radical metabolites formed or the rate at which they were formed by microsomes from rats pretreated 24 h in advance with 5 mg/kg Zn(II) or Cr(III). Extraction of rat liver with 2:1 chloroform/methanol 1 h after the administration of a 0.8 mL/kg intraperitoneal or intragastric dose of CCl4 also revealed no difference in the amount of trichloromethyl radical spin trapped in vivo following pretreatment with either Zn(II) or Cr(III). These results suggest that pretreatment with either Zn(II) or Cr(III) does not affect CCl4 metabolism nor does the MT significantly scavenge the trichloromethyl free radical metabolite.
Article
Studies of the metabolism of thyroxine in 14 cases of cirrhosis revealed a variety of deviations from normal. In addition to radiothyroxine turnover studies, determinations were made of the free thyroxine fractions and free thyroxine iodine concentrations in serum (magnesium precipitation method) as well as the maximal binding capacities of thyroxine-binding alpha globulin (TBG) and thyroxine-binding prealbumin (TBPA) by reverse flow paper electrophoresis in a glycine acetate system at pH 8.6.All cases of cirrhosis exhibited diminutions in TBPA capacities but their TBG capacities showed a wide scatter (13.4 to 41.6 mug/100 ml). The free thyroxine fraction was quite variable, with distinct elevations in nine of the 17 sera.The binding proteins appeared to be determinants of the free thyroxine fraction, which in turn, appeared to be a direct determinant of the half-time of turnover. These inferences did not exclude other possible factors including diminished hepatic uptake and metabolism of the hormone in liver disease.Despite considerable alterations in biological half-times, free thyroxine values, and binding proteins, it was remarkable that the absolute hormone disposal was normal in all 14 patients with cirrhosis.