SUPEROXIDE DISMUTASE IN JUVENILE NEURONAL CEROID-LIPOFUSCINOSIS (SPIELMEYER-VOGT-BATTEN'S DISEASE)

Abstract— The ceroid-lipofuscin pigments found in neuronal ceroid-lipofuscinosis are believed to arise from lipid peroxidation-damaged organelle membranes. In several in vitro systems superoxide dismutase inhibits lipid peroxidation. Erythrocytes and lymphocytes were prepared from ten patients with juvenile neuronal ceroid-lipofuscinosis (Spielmeyer-Vogt-Batten's disease). Copper-zinc and manganese superoxide dismutases were selectively assayed by a direct method on homogenates of the cells. No significant differences were found between the patients, neurological controls and healthy adults.     

Superoxide anion generation, erythrocytes superoxide dismutase activity, and lipid peroxidation during hemoperfusion and hemodialysis in chronic uremic patients

In 11 chronic uremic patients superoxide anion generation in whole blood, both without and with opsonized zymosan stimulation, was lower than that in 11 healthy controls, while erythrocyte superoxide dismutase (SOD-1) activity and erythrocyte and plasma malonyldialdehyde (MDA) concentrations were elevated. During hemoperfusion (HP) and hemodialysis (HD) superoxide anion generation transiently significantly increased. Changes in the erythrocyte SOD-1 activity and plasma and erythrocyte MDA concentrations during HP suggested that this procedure exerted beneficial effects on lipid peroxidation. On the other hand, during HD erythrocyte membrane lipid peroxidation seemed to be enhanced even further; this phenomenon took place mainly within the dialyzer and a decrease in the erythrocyte SOD-1 activity seemed to be one of the contributing factors. Results of in vitro experiments with cross-incubation of erythrocytes and blood plasma and incubation of whole blood with cuprophan membrane suggest existence of an SOD-1 activator in the uremic blood plasma, which is possibly eliminated during HD.     

Interrelationship of antioxidative status, lipid peroxidation, and lipid profile in insulin-dependent and non-insulin-dependent diabetic patients

This study aimed to investigate the interrelationship of plasma lipid profile, lipid peroxidation, and erythrocyte antioxidative defense in patients with insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetes mellitus. Plasma levels of total cholesterol, triglycerides, and lipid peroxides and the activities of copper, zinc superoxide dismutase (CuZnSOD), catalase, glutathione peroxidase (GSH-Px), as well as the amount of glutathione in erythrocytes, were determined in IDDM, NIDDM, and nondiabetic control subjects. Additionally, morphology of erythrocytes in all subjects was examined. Plasma levels of total cholesterol and triglycerides were significantly increased in NIDDM compared with controls. Also, the lipid peroxide level was higher in NIDDM than in either control or IDDM subjects. CuZnSOD activity in erythrocytes was elevated in NIDDM patients compared with the control. In NIDDM patients, more extensive erythrocyte spherocytosis and echinocytosis compared with both control and IDDM subjects were observed. In contrast with the IDDM group, the observed abnormality in lipid metabolism in NIDDM patients is closely associated with increased lipid peroxidation, changes in antioxidative defense, and erythrocyte morphology.     

Product of extracellular-superoxide dismutase catalysis

Extracellular-superoxide dismutase is a tetrameric enzyme containing four copper atoms. It has previously been shown to catalyse the decay of the superoxide radical, but the resulting product was not determined. In a xanthine oxidase-xanthine system in which about 30% of the electron flux resulted in superoxide radical formation, accumulation of hydrogen peroxide was determined. Catalysis of superoxide radical decay by extracellular-superoxide dismutase was found to result in hydrogen peroxide formation. The catalysed reaction is thus identical to those of previously investigated superoxide dismutases. Human manganese superoxide dismutase was also found to dismute the superoxide radical to hydrogen peroxide and water.     

Effect of dialysis on oxidative stress in uraemia

It has been postulated that dialysis of patients with chronic renal failure (CRF) is associated with increased lipid peroxidation which may contribute to vascular and other complications of the syndrome. In the present study, a specific and precise technique [ferrous oxidation in xylenol orange (FOX) assay] was used to measure plasma lipid hydroperoxides (ROOHs) in three groups of uraemic patients. Patients were either studied before starting dialysis (n = 12) or on continuous ambulatory peritoneal dialysis (CAPD, n = 12) or haemodialysis (HD, n = 36) and compared to healthy controls (n = 20). Plasma ROOHs were markedly elevated in HD patients compared with the controls (7.01 +/- 2.9 microM versus 4.25 +/- 2.05 microM; P < 0.005, Mann-Whitney test). Plasma ROOH concentrations in the CAPD patients were increased but not significantly higher than controls (5.36 +/- 3.56 microM versus 4.25 +/- 2.05 microM). By contrast, no differences in ROOH levels were found between controls and predialysis patients. There was no difference in plasma thiobarbituric acid reactive substances (TBARS) between control and the three CRF groups. Absolute and cholesterol standardised plasma alpha-tocopherol levels were lower in the patients (whether they were on dialysis or not) than in the controls (18.62 +/- 6.88 microM versus 22.73 +/- 5.33 microM; P < 0.01 and 1.99 +/- 1.88 microM/mM versus 5.25 +/- 1.0 microM/mM; P < 0.0005, respectively). This study provides direct evidence that enhanced oxidative stress in CRF patients is related to the dialysis treatment rather than the disease itself. Further studies will be necessary to establish the relationships between plasma measures of oxidative stress and cardiovascular complications in CRF patients under dialysis and whether treatment with antioxidants may reduce oxidative stress or reverse adverse effects associated with dialysis.     

The effects of peritoneal dialysis and hemodialysis on serum tumor necrosis factor-alpha, interleukin-6, interleukin-10 and C-reactive-protein levels

BACKGROUND: Markers of an acute phase reaction, such as C-reactive protein (CRP) or tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6, are predictive for cardiovascular morbidity and mortality in normal subjects and in chronic renal failure patients. In this study, we aimed to investigate serum TNF-alpha, IL-6, IL-10 and CRP levels in continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) patients. MATERIALS AND METHODS: Serum levels of TNF-alpha, IL-6, IL-10 and CRP levels were measured in 30 patients who were just diagnosed with end-stage renal failure and treated, with 16 CAPD (nine female, seven male) and 14 HD (eight female, six male) patients, before CAPD or HD treatment and after 3 months from the beginning of CAPD or HD in patients with no clinical signs of infection. The control groups were 20 healthy persons of similar age and sex. Serum levels of TNF-alpha, IL-6, IL-10 and CRP were measured by enzyme-linked immunosorbent assay in stable CAPD and HD patients and in healthy persons. RESULTS: The mean serum levels of TNF-alpha, IL-6, IL-10 and CRP showed no significant differences between the CAPD and HD patients for the beginning values and the third month of treatment. However, serum TNF-alpha, IL-6, IL-10 and CRP levels were higher than the control group in the CAPD and HD patients regarding the beginning values and the third month of treatment (p < 0.001). CONCLUSIONS: CAPD and HD of the renal replacement therapy have no effects on serum CRP and cytokines.     

Membrane lipid changes in erythrocytes, liver and kidney in acute and chronic experimental liver disease in rats

Lipid molecules in lipoprotein surfaces exchange with their counterparts in cell plasma membranes. In human or experimental liver disease, plasma lipoprotein surfaces are enriched in cholesterol and deficient in arachidonate; corresponding alterations occur in membrane lipids of erythrocytes. To determine whether similar changes take place in membranes of nucleated cells, the lipid content of plasma and of erythrocyte, liver and kidney membranes was measured in rats with acute (3-day) galactosamine-induced hepatitis or chronic (3-week) biliary obstruction. In both models of liver injury the cholesterol:phospholipid ratio in plasma and in erythrocytes was significantly increased (P less than 0.001). Although this ratio was also elevated in liver and kidney microsomes, only in liver microsomes of obstructed rats was the increase significant (P less than 0.001). However, the cholesterol:phospholipid ratio of kidney brush-border membranes, was significantly higher in bile-duct-ligated rats; presumably, compensating mechanisms limit cholesterol accumulation in intracellular membranes. Kidney brush-border membranes from obstructed rats were deficient in arachidonate as were plasma and erythrocytes. However, arachidonate levels were unchanged in kidney microsomes; renal delta 6-desaturase, the rate-limiting enzyme in the conversion of linoleic acid to arachidonic acid, was increased by 50% (P less than 0.001) and may have counteracted a reduced supply of exogenous lipoprotein arachidonate. We conclude that in experimental liver disease lipoprotein-induced lipid abnormalities can occur in renal membranes, although compensatory mechanisms may operate; the alterations seen, cholesterol accumulation and arachidonate depletion, would be expected to interfere with sodium transport and prostaglandin production, respectively. Our findings support the hypothesis that lipid abnormalities in kidney membranes contribute to the renal dysfunction which is a frequent complication of human liver disease.     

Inhibitory effects of a manganese superoxide dismutase isolated from garlic (Allium sativum L.) on in vitro tumoral cell growth

Reactive oxygen species are implicated in cancer development and antioxidants in general and superoxide dismutases and superoxide dismutase mimetic in particular, and they inhibit malignant transformation. We examinate the effects of an isolated manganese superoxide dismutase from a medicinal plant Allium sativum. The protein was prepared by a serial of chromatographic techniques: gel filtration and diethylaminoethyl ions exchanger. The enzyme has a specific activity equal to 55 U/mg. Two tumoral cell lines, porcine endothelial cells and mouse melanoma cells were exposed to garlic superoxide dismutase. The exogenous manganese superoxide dismutase is able to modify the intracellular level of reactive oxygen species by eliminating superoxide anion and producing hydrogen peroxide. The cell viability of the two lines was not significantly affected but the cell multiplication was arrested. This effect obtained in the presence of manganese superoxide dismutase correlates with the activation and modulation of phospho‐extracellular signal‐regulated kinases proteins, implicated in the control of several biological processes including cell proliferation. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Could cholesterol bound to haemoglobin be a missing link for the occasional inverse relationship between superoxide dismutase and glutathione peroxidase activities?

The concept of an anti-oxidant defence system as a means to prevent oxidative cell damage implies balanced activities of anti-oxidant defence enzymes. As well as positive correlations between anti-oxidant enzyme activities in human erythrocytes, it has been observed that sometimes when glutathione peroxidase activity is increased, CuZn-superoxide dismutase activity is decreased. In our current study we have examined the plasma lipid profile and the anti-oxidant defence enzymes in erythrocytes from humans, pigs, and bulls. We found that a negative correlation existed between CuZn-superoxide dismutase and glutathione peroxidase activities in human erythrocytes when the concentrations of both plasma triglycerides and total cholesterol were high. This correlation was also found in pig erythrocytes, but not in bull erythrocytes. We propose that cholesterol could affect membrane lipid peroxidation and superoxide generation in erythrocytes via the recently found fraction of cholesterol bound to haemoglobin, termed haemoglobin-cholesterol.     

Cloning and characterization of the Pseudomonas aeruginosa sodA and sodB genes encoding manganese- and iron-cofactored superoxide dismutase: demonstration of increased manganese superoxide dismutase activity in alginate-producing bacteria.

Pseudomonas aeruginosa is a strict aerobe which is likely exposed to oxygen reduction products including superoxide and hydrogen peroxide during the metabolism of molecular oxygen. To counterbalance the potentially hazardous effects of elevated endogenous levels of superoxide, most aerobic organisms possess one or more superoxide dismutases or compounds capable of scavenging superoxide. We have previously shown that P. aeruginosa possesses both an iron- and a manganese-cofactored superoxide dismutase (D. J. Hassett, L. Charniga, K. A. Bean, D. E. Ohman, and M. S. Cohen, Infect. Immun. 60:328-336, 1992). In this study, the genes encoding manganese (sodA)- and iron (sodB)- cofactored superoxide dismutase were cloned by using a cosmid library of P. aeruginosa FRD which complemented an Escherichia coli (JI132) strain devoid of superoxide dismutase activity. The sodA and sodB genes of P. aeruginosa, when cloned into a high-copy-number vector (pKS-), partially restored the aerobic growth rate defect, characteristic of the Sod- strain, to that of the wild type (AB1157) when grown in Luria broth. The nucleotide sequences of sodA and sodB have open reading frames of 612 and 579 bp that encode dimeric proteins of 22.9 and 21.2 kDa, respectively. These data were also supported by the results of in vitro expression studies. The deduced amino acid sequence of the P. aeruginosa manganese and iron superoxide dismutase revealed approximately 50 and 67% similarity with manganese and iron superoxide dismutases from E. coli, respectively. There was also remarkable similarity with iron and manganese superoxide dismutases from other phyla. The mRNA start site of sodB was mapped to 174 bp upstream of the ATG codon. A likely promoter with similarity to the -10 and -35 consensus sequence of E. coli was observed upstream of the ATG start codon of sodB. Regions sequenced 519 bp upstream of the sodA electrophoresis, sodA gene revealed no such promoter, suggesting an alternative mode of control for sodA. By transverse field electrophoresis, sodA and sodB were mapped to the 71- to 75-min region on the P. aeruginosa PAO1 chromosome. Strikingly, mucoid alginate-producing bacteria generated greater levels of manganese superoxide dismutase than nonmucoid revertants, suggesting that mucoid P. aeruginosa is responding to oxidative stress and/or changes in the redox status of the cell.     

Structural identity between the iron- and manganese-containing superoxide dismutases

We have recently reported the first complete amino acid sequence of an iron-containing superoxide dismutase. The iron enzyme is thought to be closely homologous to the manganese-containing superoxide dismutases. The availability of complete amino acid sequence information for four manganese superoxide dismutases and the crystal structures for two iron and two manganese superoxide dismutases prompted us to investigate the degree of homology between the two proteins at various levels. We report that it is not possible to clearly distinguish the two proteins on the basis of their secondary or tertiary structures. It would appear that a small number of single site substitutions are responsible for conferring distinguishing properties between the two proteins. Substitution of glycine 77 and glutamine 154 by a glutamine and an alanine respectively in Photobacterium leiognathi iron superoxide dismutase may distinguish the kinetic and other particular properties of this protein from the manganese protein (and other iron superoxide dismutases). Furthermore the primary structure of both the iron and manganese proteins does not appear to have any homology with any other known amino acid sequence.     

Iron-containing superoxide dismutase from Crithidia fasciculata. Purification, characterization, and similarity to Leishmanial and trypanosomal enzymes

Leishmania tropica, Trypanosoma brucei, Trypanosoma cruzi, and Crithidia fasciculata have superoxide dismutases which are insensitive to cyanide and sensitive to peroxide and azide, properties characteristic of iron-containing superoxide dismutase. Studies on the superoxide dismutase of C. fasciculata have revealed that: 1) the enzyme is located in the cytosol; 2) isozymes exist; 3) the major superoxide dismutase isozyme (superoxide dismutase 2) has Mr approximately equal to 43,000 and consists of two equal-sized subunits, each of which contains 1.4 atoms of iron. Comparisons of the amino acid content of this crithidial superoxide dismutase with those of superoxide dismutases from other sources suggests that the crithidial enzyme is closely related to bacterial Fe-containing superoxide dismutases, and only distantly related to human Mn- and Cu,Zn-containing superoxide dismutases and to Euglena Fe-containing superoxide dismutase. Attempts are now underway to develop specific inhibitors of the trypanosomatid superoxide dismutase which may be of use in the treatment of leishmaniasis or trypanosomiasis.     

Effect of dialysis on oxidative stress in uraemia

Abstract

It has been postulated that dialysis of patients with chronic renal failure (CRF) is associated with increased lipid peroxidation which may contribute to vascular and other complications of the syndrome. In the present study, a specific and precise technique [ferrous oxidation in xylenol orange (FOX) assay] was used to measure plasma lipid hydroperoxides (ROOHs) in three groups of uraemic patients. Patients were either studied before starting dialysis (n= 12) or on continuous ambulatory peritoneal dialysis (CAPD, n= 12) or haemodialysis (HD, n= 36) and compared to healthy controls (n=20). Plasma ROOHs were markedly elevated in HD patients compared with the controls (7.01±2.9 µM versus 4.25±2.05 µM; P < 0.005, Mann-Whitney test). Plasma ROOH concentrations in the CAPD patients were increased but not significantly higher than controls (5.36±3.56 µM versus 4.25±2.05 µM). By contrast, no differences in ROOH levels were found between controls and predialysis patients. There was no difference in plasma thiobarbituric acid reactive substances (TBARS)between control and the three CRF groups. Absolute and cholesterol standardised plasma α-tocopherol levels were lower in the patients (whether they were on dialysis or not) than in the controls (18.62±6.88 µM versus 22.73±5.33 µM; P < 0.01 and 1.99±1.88 µM/mM versus 5.25±1.0 µM/mM; P < 0.0005, respectively). This study provides direct evidence that enhanced oxidative stress in CRF patients is related to the dialysis treatment rather than the disease itself. Further studies will be necessary to establish the relationships between plasma measures of oxidative stress and cardiovascular complications in CRF patients under dialysis and whether treatment with antioxidants may reduce oxidative stress or reverse adverse effects associated with dialysis.     

Lipid peroxidation and antioxidant status in patients with periodontitis

Our aim was to assess the degree of oxidative stress in patients with periodontitis by measuring their levels of thiobarbituric acid reactive substances (TBARS), enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione peroxide (GSHPx)), and non-enzymatic antioxidants (vitamins E and C, reduced glutathione (GSH)). This study was conducted on 25 adult chronic periodontitis sufferers who were patients in Rajah Muthiah Dental College and Hospital, Annamalai University. The levels of TBARS and non-enzymatic antioxidants, and the activities of enzymatic antioxidants in the patients' plasma, erythrocytes and gingival tissues were assayed using specific colorimetric methods. The periodontitis sufferers had a significantly higher TBARS level than the healthy subjects. In the plasma, erythrocytes, erythrocyte membranes and gingival tissues of the periodontitis sufferers, enzymatic antioxidant activities were found to be significantly higher, whereas the levels of non-enzymatic antioxidants were significantly lower (except for reduced glutathione in the gingival tissues) relative to the parameters found for healthy subjects. The disturbance in the endogenous antioxidant defense system due to over-production of lipid peroxidation products at inflammatory sites can be related to a higher level of oxidative stress in patients with periodontitis.     

Protective effects of topical alpha-tocopherol acetate on UVB irradiation in guinea pigs: importance of free radicals

Reactive oxygen species can be generated by daily exposure of the skin to ultraviolet light and may cause some subchronic and chronic skin disorders. The aim of this study was to investigate a possible preventive role of alpha-tocopherol acetate (ATA) on ultraviolet B (UVB) induced peroxidation by assessing lipid peroxide (LPO) levels and activity of reactive oxygen scavenging enzymes including glutathione peroxidase and superoxide dismutase (SOD) in guinea pigs. ATA was topically applied to the skin for three weeks before a single dose of 0.9 J/cm2 UVB irradiation on the skin and lipid peroxide levels and antioxidants in plasma, skin and liver and erythrocytes were determined after decapitation. Topical application of ATA prevented the UVB irradiation-induced reduction of scavenging enzyme activities in skin and erythrocytes. In conclusion, we suggest that topical applications of ATA before UVB irradiation is effective in protecting the skin from unwanted effects of UVB irradiation.     

Superoxide Dismutase and Oxygen Metabolism in Streptococcus faecalis and Comparisons with Other Organisms

Streptococcus faecalis contains a single superoxide dismutase that has been purified to homogeneity with a 55% yield. This enzyme has a molecular weight of 45,000 and is composed of two subunits of equal size. It contains 1.3 atoms of manganese per molecule. Its amino acid composition was determined and is compared with that for the superoxide dismutases from Escherichia coli, Streptococcus mutans, and Mycobacterium lepraemurium. When used as an antigen in rabbits, the S. faecalis enzyme elicited the formation of a precipitating and inhibiting antibody. This antibody cross-reacted with the superoxide dismutase present in another strain of S. faecalis, but neither inhibited nor precipitated the superoxide dismutases in a wide range of other bacteria, including several other streptococci, such as S. pyogenes, S. pneumoniae, and S. lactis. The inhibiting antibody was used to suppress the superoxide dismutase activity present in cell extracts of S. faecalis and thus allow the demonstration that 17% of the total oxygen consumption by such extracts, in the presence of reduced nicotinamide adenine dinucleotide, was associated with the production of O(2) (-). A variety of bacterial species were surveyed for their content of superoxide dismutases. The iron-containing enzyme was distinguished from the manganese-containing enzyme through the use of H(2)O(2), which inactivates the former more readily than the latter. Some of the bacteria appeared to contain only the iron enzyme, others only the manganese enzyme, and still others both. Indeed, some had multiple, electrophoretically distinct superoxide dismutases in both categories. There was no discernible absolute relationship between the types of superoxide dismutases in a particular organism and their Gram-stain reaction.     

Superoxide dismutase activity in early stages of development in normal and dystrophic chickens

Changes in superoxide dismutase activities in early stages of chronological development were investigated in normal and dystrophic chickens. Both cupro-zinc and manganese superoxide dismutase activities were significantly elevated in the dystrophic chickens studied as early as one week after hatching compared to those in the control. In control chickens, both cupro-zinc and manganese superoxide dismutase activities declined as they grew older. In dystrophic chickens, manganese superoxide dismutase activity declined gradually as they grew older as in the control. However, cupro-zinc superoxide dismutase activity increased until four weeks of age. The latter activity was still twice as high as that of the control at four months of age. Increased activities in superoxide dismutases in early stages of the development suggest presence of increased turnover of active oxygen species from the early stage of the disease in this avian muscular dystrophy. And the distinct time course of cupro-zinc superoxide dismutase activity suggests involvement of active oxygen species in pathogenesis of this disorder.     

Superoxide dismutases—a review of the metal-associated mechanistic variations

Superoxide dismutases are enzymes that function to catalytically convert superoxide radical to oxygen and hydrogen peroxide. These enzymes carry out catalysis at near diffusion controlled rate constants via a general mechanism that involves the sequential reduction and oxidation of the metal center, with the concomitant oxidation and reduction of superoxide radicals. That the catalytically active metal can be copper, iron, manganese or, recently, nickel is one of the fascinating features of this class of enzymes. In this review, we describe these enzymes in terms of the details of their catalytic properties, with an emphasis on the mechanistic differences between the enzymes. The focus here will be concentrated mainly on two of these enzymes, copper, zinc superoxide dismutase and manganese superoxide dismutase, and some relatively subtle variations in the mechanisms by which they function.     

Manganese superoxide dismutase from a higher plant

A manganese-containing superoxide dismutase (EC 1.15.1.1) was purified to homogeneity from a higher plant for the first time. The enzyme was isolated fromPisum sativum leaf extracts by thermal fractionation, ammonium sulfate salting out, ion-exchange and gel-filtration column chromatography, and preparative polyacrylamide gel electrophoresis. Pure manganese superoxide dismutase had a specific activity of about 3,000 U mg^-1 and was purified 215-fold, with a yield of 1.2 mg enzyme per kg whole leaf. The manganese superoxide dismutase had a molecular weight of 94,000 and contained one g-atom of Mn per mol of enzyme. No iron and copper were detected. Activity reconstitution experiments with the pure enzyme ruled out the possibility of a manganese loss during the purification procedure. The stability of manganese superoxide dismutase at-20°C, 4°C, 25°C, 50°C, and 60°C was studied, and the enzyme was found more labile at high temperatures than bacterial manganese superoxide dismutases and iron superoxide dismutases from an algal and bacterial origin.Abbreviations NBT nitro blue tetrazolium - SOD superoxide dismutase (EC 1.15.1.1)     

Expression of antioxidant enzymes in rat kidney during ischemia-reperfusion injury

The effect of ischemia-reperfusion on activity, protein and m-RNA levels of catalase, copper-zinc and manganese containing superoxide dismutases and glutathione peroxidase, the enzymes that are involved in free radical detoxification was studied in rat kidney. Ischemia alone did not alter either the activities or protein levels of superoxide dismutase and glutathione peroxidase. However, catalase activity was found to be inhibited to 82% of control. The inhibition of catalase was due to the inactivation of the enzyme as there was no significant change in enzyme protein level. Reperfusion following ischemia, however, led to a significant decrease in both the activities as well as the protein levels of all the antioxidant enzymes. The observed overall decrease in total superoxide dismutase activity was the net effect of a decrease in copper-zinc superoxide dismutase while manganese superoxide dismutase activity was found to be increased following reperfusion. This observed increased manganese superoxide dismutase activity was the result of its increased protein level. The mRNA levels for catalase, superoxide dismutases, and glutathione peroxidase were observed to be increased (100–145% of controls) following ischemia; reperfusion of ischemic kidneys, however, resulted in a significant decrease in the levels of mRNAs coding for all the enzymes except manganese superoxide dismutase which remained high. These results suggest that in tissue, the down regulation of the antioxidant enzyme system could be responsible for the pathophysiology of ischemia-reperfusion injury.