Changed cellular membrane lipid composition and lipid peroxidation of kidney in rats with chronic fluorosis

An animal model of chronic fluorosis was produced by subjecting Wistar rats to high doses of fluoride in drinking water for a prolonged period. Phospholipid and neutral lipid contents in rat kidney were then analyzed by high-performance liquid chromatography (HPLC), and fatty acid compositions from individual phospholipids were measured by gas chromatography. Lipid peroxidation was detected by the thiobarbituric-acid-reactive substance assay. Results showed that the total phospholipid content significantly decreased in the kidney of the rats treated with high doses of fluoride and the main species influenced were phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Decreased proportions of polyunsaturated fatty acids were observed in PE and PC in kidney of fluoride-treated animals compared to controls. No changes could be detected in the amounts of cholesterol and dolichol in kidneys between the rats treated with fluoride and controls. A significant decrease of ubiquinone in rat kidney was observed in the groups treated with excessive fluoride. High levels of lipid peroxidation were detected in kidney of the rats with fluorosis. It is plausible that the specific modification of lipid composition results from lipid peroxidation. The oxidative stress and modification of cellular membrane lipids may be involved in the pathogenesis of chronic fluorosis and provide a possible explanation for the gross system damage observed in the body, especially in soft tissues and organs.     

Chronic fluoride toxicity and myocardial damage: antioxidant offered protection in second generation rats

This experiment was designed to investigate the extent of peroxidative changes and histological alterations in the myocardium of rats exposed to high fluoride for two generations, in addition to ameliorative role of selenium and vitamin E on the above indices. Adult albino Wistar rats were given fluoride through drinking water (200 ppm F) and maintained subsequently for two generations, while they were exposed to fluoride throughout the experiment. Fluoride treatment significantly increased the lipid peroxidation and decreased the activity of antioxidant enzymes, viz., catalase, superoxide dismutase, and glutathione level in auricle and ventricle regions of the heart. Decreased feed and water consumption, organ somatic index and marginal drop in body growth rate were observed. Decreased antioxidant enzymes and increased malondialdehyde levels might be related to oxidative damage that occurs variably in the myocardium of rats. Biochemical changes were supported by the histological observations, which also revealed that chronic exposure to fluoride causes damage to the myocardium. Results of this study can be taken as an index of cardio-toxicity in rats exposed to water fluoridation. Further, oral supplementation of selenium and vitamin E not only inhibited oxidative stress but also enhanced the activities of antioxidant enzymes. Administration of antioxidants during fluoride exposure significantly overcame cardiac fluoride toxicity and therefore may be a therapeutic strategy for fluorotic victims.     

Effects of ascorbic acid and alpha-tocopherol on arsenic-induced oxidative stress

Arsenic is an ubiquitous element in the environment causing oxidative burst in the exposed individuals leading to tissue damage. Antioxidants have long been known to reduce the free radical-mediated oxidative stress. Therefore, the present study was designed to determine whether supplementation of alpha-tocopherol (400 mg/kg body weight) and ascorbic acid (200 mg/kg body weight) to arsenic-intoxicated rats (100 ppm in drinking water) for 30 days affords protection against the oxidative stress caused by the metalloid. The arsenic-treated rats showed elevated levels of lipid peroxide, decreased levels of non-enzymatic antioxidants and activities of enzymatic antioxidants. Administration of alpha-tocopherol and ascorbic acid to arsenic-exposed rats showed a decrease in the level of lipid peroxidation (LPO) and enhanced levels of total sulfhydryls, reduced glutathione, ascorbic acid and alpha-tocopherol and so do the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase to near normal. These findings suggest that alpha-tocopherol and ascorbic acid prevent LPO and protect the antioxidant system in arsenic-intoxicated rats.     

Aqueous extract of the bark of <Emphasis Type="Italic">Terminalia arjuna</Emphasis> plays a protective role against sodium-fluoride-induced hepatic and renal oxidative stress

Fluoride is an environmental and industrial pollutant. It has already been reported that the accumulation of fluoride can alter the activities of some enzymes involved in the free-radical metabolism and also decrease the activities of some enzymes involved in the antioxidant defense system. In the present study, we have investigated the antioxidative properties of aqueous extract of the bark of Terminalia arjuna (TA) on sodium fluoride (NaF) induced oxidative damages in the livers and kidneys of Swiss albino mice. The mice were treated with 600 ppm NaF for one week in drinking water and the activities of antioxidant enzymes, like superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST), and the levels of non-protein thiol, reduced glutathione (GSH), along with lipid peroxidation in the liver and kidney, were determined. Fluoride administration significantly altered the levels of all of the factors compared to that of normal mice. Dose- and time-dependent studies suggest that the aqueous extract of the bark of TA showed optimum protective activity against NaF-induced oxidative damages at a dose of 40 mg/kg body weight for 10 days. Oral administration of the extract for the specified dose and time followed by NaF treatment (600 ppm) normalized the levels of the hepatic and renal antioxidant enzymes, GSH, and lipid peroxidation significantly to almost normal levels. The effects of a known antioxidant, vitamin E, and a non-relevant agent, bovine serum albumin (BSA), have also been included in the study. In addition, TA extract has been found to possess radical scavenging activity. Combining all of the data, the results suggest that TA might possess a protective role against NaF-induced hepatic and renal oxidative damages, probably via its antioxidant properties. Mahua Sinha and Prasenjit Manna contributed equally in the study.     

Effect of long term fluoride exposure on lipid composition in rat liver

Chronic fluorosis can severely damage many systems of human body, but its pathogenesis is unclear. Normal composition and structure of cellular membrane lipids are a basic factor to maintain cell function. In this investigation, cellular membrane lipids of the liver were analysed after a long term fluoride treatment for rats and the results are discussed in order to give an explanation for the pathogenesis of this disease. Wistar rats were supplied with drinking water containing either 30 or 100 ppm fluoride (NaF) for seven months. Contents of phospholipid and neutral lipid in rat liver were analyzed by high-performance liquid chromatography, and fatty acid composition from individual phospholipids was measured by gas chromatography. Results showed that the total liver phospholipid content decreased in the rats treated with high dose of fluoride due to a lower content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylserine (PS). Among the fatty acid compositions of PE and PC in the livers of fluoride poisoned animals, the proportion of polyunsaturated fatty acids (20:4 and 22:6) decreased, whereas saturated fatty acids (16:0 and 18:0) increased. No changes could be detected in the amounts of liver cholesterol and dolichol. Total ubiquinone contents in rat liver were reduced by 11% in the group treated with 30 ppm fluoride and by 42% in the group treated with 100 ppm fluoride. In the subclasses of ubiquinone, both ubiquinone-9 and ubiquinoine-10 amounts decreased after fluoride treatment. These modifications of membrane lipids might be induced by oxidative stress, which might be an important factor in the pathogenesis of chronic fluorosis.     

Oxidative stress might be a mechanism connected with the decreased α7 nicotinic receptor influenced by high-concentration of fluoride in SH-SY5Y neuroblastoma cells

The possible mechanism concerning decreased alpha 7 nicotinic acetylcholine receptor (nAChR) influenced by fluorosis was investigated. SH-SY5Y cells were exposed to fluoride within the range of 0.05-5 microM, or ferrous iron (1-100 microM), a free radical inducer. The levels of alpha 7 nAChR expression, lipid peroxidation and protein oxidation were detected. The results showed that both high-concentrations of fluoride and ferrous iron induced increased levels of lipid peroxidation and protein oxidation in SH-SY5Y cells with concentration-dependent manners. In addition, inhibition of alpha 7 nAChR at protein level was observed in the cells exposed to high amounts of fluoride or ferrous iron. Furthermore, a declined value of Bmax in [125I]alpha-bungarotoxin binding sites was found in the cells treated with the high-concentration of fluoride. Interestingly, antioxidants (vitamin E and glutathione) can attenuate the inhibition of the receptor induced by fluoride. These findings suggest that oxidative stress resulted from fluorosis might directly induce the deficit of alpha 7 nAChR.     

Influence of repeated preexposure to arsenic on acetaminophen-induced oxidative stress in liver of male rats

We evaluated whether repeated arsenic preexposure can increase acetaminophen-induced hepatic oxidative stress. Rats were exposed to arsenic (25 ppm; rat equivalent concentration of maximum groundwater contamination level) via drinking water for 28 days. Next day, they were given single oral administration of acetaminophen (420 or 1000 mg/kg b.w.). Hepatotoxicity was evaluated by assessing serum biomarkers, cytochrome-P450 (CYP) content, CYP3A4- and CYP2E1-dependent enzymes, lipid peroxidation and antioxidants. Arsenic or acetaminophen increased serum ALT and AST activities and depleted CYP. Arsenic decreased, but acetaminophen increased CYP-dependent enzyme activities. These agents independently increased lipid peroxidation and decreased antioxidants. Arsenic did not alter the effects of acetaminophen on serum biomarkers, caused further CYP depletion and decreased acetaminophen-mediated induction of drug-metabolizing enzymes. Arsenic enhanced the lower dose of acetaminophen-mediated lipid peroxidation and glutathione depletion with no further alterations in enzymatic antioxidants. However, arsenic attenuated the higher dose-mediated lipid peroxidation and glutathione depletion with improvement in glutathione peroxidase and glutathione reductase activities, further decrease in catalase and no alterations in superoxide dismutase and glutathione-S-transferase activities. Results show that arsenic preexposure increased the susceptibility of rats to hepatic oxidative stress induced by the lower dose of acetaminophen, but reduced the oxidative stress induced by the higher dose.     

Fluoride levels and dental fluorosis in two districts in Zimbabwe.

Water from two rural communities in Zimbabwe was analysed for fluoride content and school children in the two districts were examined for dental fluorosis. The survey for fluoride distribution in drinking water and the survey for the prevalence of fluorosis in the two districts were two complementary phases of the same project. In Gokwe District, water from artesian wells was found to contain between 5ppm and 10ppm fluoride ion concentration and as a result, fluorosis was found to be extremely severe in those communities solely dependent on artesian wells. In Chimanimani District, water from hot springs was found to contain five to six ppm fluoride ion concentration and in the catchment area of schools, drinking from hot springs fluorosis was also found to be very severe. In both cases, access to high fluoride water can be linked to administrative decisions taken some thirty years ago. Consideration for the long-term adverse effects of drinking water with excess fluoride had not been taken and now, corrective action will need to incorporate inter-disciplinary expertise.     

Effect of fluoride intoxication on lipidperoxidation and antioxidant status in experimental rats

Fluoride is a potent enzyme poison. Thirty ground water samples from Vellore District, Tamil Nadu, India were analysed for fluoride content and it was revealed that the fluoride content of 24 samples were over and above the permissible limits. In the present study, the experimental rats were orally treated with 25 ppm of fluoride/rat/day for 8 and 16 weeks, respectively, and the levels of lipid peroxidation and antioxidant enzymes were studied to evaluate fluoride intoxication. An increase in the level of lipid peroxides along with a concomitant decrease in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione content were observed in fluoride administered groups of rats. The altered antioxidant status may be attributed to the increased generation of free radicals.     

Influence of selenium and/or magnesium on alleviation alcohol induced oxidative stress in rats, normalization function of liver and changes in serum lipid parameters

The aim of this study was to evaluate the attenuating effect of given selenium and/or magnesium on ethanol-induced oxidative stress, disturbances of liver function and cholesterol metabolism. Forty male rats were divided into five groups: C - control, Et - intoxicated with alcohol (15% solution in drinking water), Et + Mg, Et + Se, Et + Mg + Se - intoxicated with alcohol and supplemented with selenium (0.4 mg Se/l water), magnesium (100 mg Mg/l water) and combination of Se and Mg, respectively. The experiment was carried out over the 3 months. The results show that the chronic ingestion of alcohol induces lipid peroxidation and histopathological changes in liver. Supplementation with magnesium only partially alleviates oxidative stress and damages in this tissue. The both selenium alone and combination of magnesium and selenium significantly elevated total antioxidant status (TAS) in serum, activity of glutathione peroxidase and ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) in liver and retarded oxidative stress and histopathological changes in this tissue. Chronic administration of ethanol (alone and with magnesium) resulted in significant decrease in the serum total cholesterol and retardation in the body weight gain in comparison with the control group. In the groups supplemented with selenium and selenium and magnesium simultaneously, concentration of total cholesterol in serum and body gains was similar to the control group. Supplementation of Se or selenium and magnesium simultaneously significantly enhances antioxidant defence and is more effective against alcohol-induced oxidative stress, disturbance of liver function and cholesterol metabolism than the separate use of magnesium.     

A mechanism of paraquat toxicity in mice and rats.

The purpose of this study was to investigate the hypothesis that paraquat toxicity results from cyclic reduction-oxidation of paraquat in vivo, with subsequent generation of superoxide radicals and initiation of lipid peroxidation. Phenobarbital pretreatment (0.1% in drinking water for 10 days) significantly increased the paraquat LD50 in mice, but only when the mice were continued on phenobarbital after paraquat administration. Phenobarbital, through its own metabolism, may be competing for electrons which might otherwise be utilized in paraquat reduction and thus decrease paraquat toxicity. Paraquat, given at 30 mg/kg ip to mice, significantly decreased liver concentrations of the water-soluble antioxidant, reduced glutathione, and lung concentrations of lipid-soluble antioxidants. The decrease in tissue antioxidants may reflect the initiation of lipid peroxidation by paraquat. Oxygen-tolerant rats (exposure to 85% oxygen for 7 days) have increased activities of pulmonary enzymes which combat lipid peroxidation. The paraquat Lt50 (median time to death) after 45 mg/kg of paraquat ip was significantly increased in oxygentolerant rats compared to room-air-exposed controls. Rats exposed to 100 ppm paraquat in the drinking water for 3 weeks had significantly elevated activities of lung glucose-6-phosphate dehydrogenase and glutathione reductase. The cross-tolerance of oxygen and paraquat and the induction by paraquat of pulmonary enzymes that supply reducing equivalents to combat oxidative damage support the proposal that paraquat may initiate lipid peroxidation in vivo.     

Berberine protects liver from ethanol-induced oxidative stress and steatosis in mice

Alcohol consumption is customary in many cultures and it is a common human behavior worldwide. Binge ethanol and chronic alcohol consumption, two usual drinking patterns of human beings, produce a state of oxidative stress in liver and disturb the liver function. However, a safe and effective therapy for alcoholic liver disease in humans is still elusive. This study identified the natural product berberine as a potential agent for treating or preventing ethanol-induced liver injury. We demonstrated that berberine attenuated oxidative stress resulted from binge drinking in liver by reducing hepatic lipid peroxidation, glutathione exhaust and mitochondrial oxidative damage. Furthermore, berberine also prevented the oxidative stress and macrosteatosis in response to chronic ethanol exposure in mice. Either the total cytochrome P450 2E1 or the mitochondria-located cytochrome P450 2E1, which is implicated in ethanol-mediated oxidative stress, was suppressed by berberine. On the other hand, berberine significantly blunted the lipid accumulation in liver due to chronic alcohol consumption, at least partially, through restoring peroxisome proliferator-activated receptor α/peroxisome proliferator-activated receptor-gamma Co-activator-1α and hepatocyte nuclear factor 4α/microsomal triglyceride transfer protein pathways. These findings suggested that berberine could serve as a potential agent for preventing or treating human alcoholic liver disease.     

Cataractogenic Effect of Fluorosis in an Animal Model

Endemic fluorosis is a chronic, crippling, skeletal and dental disease caused by ingesting large amounts of fluoride either through water or rarely from foods of endemic areas. Although systemic disorders of fluorosis have a wide variety of appearances, little attention has been given to the spectrum of lenticular findings.

Thirty rats were given commercially available spring water either with 100 ppm fluoride (Experimental group, n=15 rats, 30 eyes) or 0.07 ppm fluoride (control group, n=15 rats, 30 eyes) for 24 weeks. The examinations revealed various levels of opacifications and histopathologic changes in 12 eyes of the high fluoride intake group, whereas none of the eyes were affected in the control group. Differences between groups were statistically significant (p<0.05).

Our study demonstrates that fluoride is a potential cataractogenic agent. Hence, we believe that dilution of fluoride in tap waters in endemic areas is an important measure for ophthalmic health. We suggest that ophthalmologic examinations should be performed on patients with documented endemic dental and skeletal fluorosis.     

Subchronic exposure to a mixture of groundwater-contaminating metals through drinking water induces oxidative stress in male rats

The current study examines the oxidative stress-inducing potential of a mixture of metals, representative of groundwater contamination in different areas of India. Male albino rats were exposed to the mixture through drinking water for 90 days at 0, 1, 10 and 100 times the mode concentrations of the metals in contaminated waters and at concentrations equal to their WHO maximum permissible limit (MPL) in drinking water. The endpoints evaluated were lipid peroxidation (LPO), GSH content and activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase in heart, liver, kidney and brain. MPL and 1× levels did not induce any alterations. The mixture at 10× and 100× doses increased LPO and decreased GSH level and activities of the antioxidases in kidney, liver and brain, but no alterations were observed in heart. An inverse correlation between LPO and GSH or antioxidaes and a positive correlation between GSH and glutathione peroxidase or glutathione reductase were found in the affected organs. The findings suggest that the mixture induces oxidative stress and decreases antioxidant status in 10× and 100× the mode concentrations of the metals in drinking water.     

Effects of fluoride on the tissue oxidative stress and apoptosis in rats: biochemical assays supported by IR spectroscopy data

The mechanism underlying the toxicity of fluoride still remains unknown. To investigate the effects of different doses of fluoride on blood and tissue oxidative stress and apoptosis, we exposed male rats to three doses of fluoride (10, 50 and 100ppm in drinking water) for a period of 10 weeks. The results suggested that exposure to 10ppm fluoride significantly increased the level of reactive oxygen species (ROS) in blood accompanied by a decrease in glutathione (GSH) level. No evidences of oxidative stress in soft tissues were seen. Fluoride (10ppm) also decreased GSH/GSSG ratio significantly. Contrary to expectation, 50 and 100ppm fluoride exposure did not produce a more pronounced toxicity in the soft tissues. However, we observed a significantly elevated concentration of ROS and depleted GSH level in blood. Exposure to fluoride did not produce any sign of apoptosis. To support our above mentioned biochemical observations and to suggest possible mechanism of action of fluoride, IR spectra of brain tissues were recorded. The results of these spectra indicated significant shift in the characteristic peak of -OH group in animals exposed to 10ppm fluoride however at higher doses, the shift was minimal. It can thus be concluded that fluoride-induced toxicity is mediated through oxidative stress particularly at a comparatively lower level of exposure however at the higher doses the mode of action still unclear and needs further investigation.     

Induction of oxidative stress in rat brain by acrylonitrile (ACN).

Chronic treatment with acrylonitrile (ACN) has been shown to produce a dose-related increase in glial cell tumors (astrocytomas) in rats. The mechanism(s) for ACN-induced carcinogenicity remains unclear. While ACN has been reported to induce DNA damage in a number of short-term systems, evidence for a genotoxic mechanism of tumor induction is the brain is not strong. Other toxic mechanisms appear to participate in the induction of tumor or induce the astrocytomas solely. In particular, nongenotoxic mechanisms of carcinogen induction have been implicated in this ACN-induced carcinogenic effect in the rat brain. One major pathway of ACN metabolism is through glutathione (GSH) conjugation. Extensive utilization and depletion of GSH, an important intracellular antioxidant, by ACN may lead to cellular oxidative stress. The present study examined the ability of ACN to induce oxidative stress in male Sprague-Dawley rats. Rats were administered ACN at concentrations of 0, 5, 10, 100, or 200 ppm in the drinking water and sampled after 14, 28, or 90 days of continuous treatment. Oxidative DNA damage indicated by the presence of 8-hydroxy-2'-deoxyguanosine (OH8dG) and lipid peroxidation indicated by the presence of malondialdehyde (MDA), a lipid peroxidation product, in rat brains and livers were examined. The levels of reactive oxygen species (ROS) were also determined in different rat tissues. Both the levels of nonenzymatic antioxidants (GSH, vitamin E) and the activities of enzymatic antioxidants (catalase, superoxide dismutase, glutathione peroxidase) in rat brains and livers were measured. Increased levels of OH8dG, MDA, and ROS were found in the brains of ACN-treated rats. Decreased levels of GSH and activities of catalase and SOD were also observed in the brains of ACN-treated rats compared to the control group. Interestingly, there were no changes of these indicators of oxidative stress in the livers of ACN-treated rats. Rat liver is not a target for ACN-induced carcinogenesis. These data indicate that ACN selectively induces oxidative stress in rat brain at doses that produce carcinogenesis in chronic treatment studies.     

Effects of aldose reductase inhibitors on antioxidant defense in rat and rabbit liver.

Aldose reductase has been implicated in the etiology of diabetic complications, atherosclerosis, and ischemia-reperfusion injury. Aldose reductase inhibitors are known to have species-dependent differences in biotransformation enzyme induction. Whether aldose reductase inhibitors, which have antioxidant potential, alter the oxidative stress pathway is unknown. This study has determined whether four daily ip treatments of either low (10 mg/kg) or high (50 mg/kg) doses of AL-1576 or AL-4114 alter the activities of the antioxidant defense enzymes catalase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and the concentrations of reduced and oxidized glutathione in livers of normal rats and rabbits. There was no change in the concentration of thiobarbituric acid reactive substances in either rat or rabbit livers, indicating that lipid peroxidation was not increased by any treatment. Hepatic catalase, superoxide dismutase, and glutathione peroxidase activities and concentrations of reduced and oxidized glutathione were not significantly altered in rat, though glutathione reductase activity was increased after high doses of both drugs. However, in rabbit liver, glutathione reductase activity decreased in a dose-dependent manner after AL-4114 treatment, while superoxide dismutase and glutathione peroxidase activities decreased only after the low dose of AL-4114. Although AL-4114 and AL-1576 did not directly generate increased lipid peroxidation within normal rat and rabbit livers, some of the enzymes responsible for oxidative defense were altered, particularly in rabbit livers.     

Impact of ursolic acid on chronic ethanol-induced oxidative stress in the rat heart

Oxidative stress plays an important role as a mediator of myocardial damage produced by ethanol. This work was designed to investigate the effect of ursolic acid (UA), a reported radical scavenger and antioxidant, on oxidative stress in the heart of chronically ethanol-administered rats. Chronic ethanol administration (7.9 g/kg/day for 60 days) caused tissue damage that was manifested by the elevation of serum lactate dehydrogenase (LDH) and creatine phosphokinase (CPK). It also induced oxidative stress in the heart by increasing the lipid peroxidation process and by decreasing the antioxidant capacity of the heart. After the induction of toxicity (i.e. initial 30 days), treatment groups received UA (10, 20 and 40 mg/kg/day) along with ethanol for another 30 days. Coadministration of UA effectively (20 mg/kg/day) restored the activities of marker enzymes. It also controlled the oxidative stress by decreasing lipid peroxidation products (manifested by decreased lipid peroxidation products such as thiobarbituric acid reactive substances--TBARS, lipid hydroperoxides--LOOH and conjugated dienes--CD), increasing the activities of free radical scavenging enzymes (superoxide dismutase--SOD, catalase--CAT, glutathione peroxidase--GPx and glutathione S-transferase--GSH) and increasing the levels of non-enzymic antioxidants such as reduced glutathione, ascorbic acid and alpha-tocopherol. These findings demonstrate that UA acts as a protective agent against ethanol-induced abnormalities in the heart by reducing the lipid peroxidation process and by enhancing the antioxidant capacity.     

Oxidative stress in heart tissue of hyperthyroid and iron supplemented rats.

This study was designed to investigate the effect of hyperthyroidism and/or iron supplementation or cardiac oxidative stress parameters--the lipid peroxidation end product glutathione (GSH), glutathione peroxidase (CSH-Px), and superoxide dismutase (CuZnSOD)--in rats. In plasma, ferritin as an indicator of iron status and glutamate oxaloacetate transaminase (GOT) as an indicator of damage to the heart tissue were analyzed. Our findings show that hyperthyroidism increased lipooxidative damage as reflected by higher lipid peroxidation end product levels and elevated antioxidant defense parameters-GSH and GSH-Px. Iron supplementation per se does not affect oxidative stress parameters studied in the euthyroid state. Although iron increased lipid peroxidation in the hyperthyroid state, this effect was less than that seen in euthyroidism. Iron supplementation to hyperthyroid rats significantly lowered plasma ferritin levels, suggesting increased iron elimination with consequently reduced oxidative stress.