Antioxidant status and lipid peroxidation in type II diabetes mellitus

Diabetes Mellitus (DM), a state of chronic hyperglycaemia, is a common disease affecting over 124 million individuals worldwide. In this study, erythrocyte glutathione levels, lipid peroxidation, superoxide dismutase, catalase, and glutathione peroxidase and some extracellular antioxidant protein levels of patients with type II diabetes mellitus and healthy controls were investigated. Thirty-eight patients (21 males; with age of mean +/- SD, 53.1+/-9.7 years) and 18 clinically healthy subjects (10 males; with age of mean +/- SD, 49.3+/-15.2 years) were included in the study. Levels of erythrocyte lipid peroxidation, serum ceruloplasmin and glucose levels, HbA1C levels, and erythrocyte catalase activity were significantly increased, whereas serum albumin and transferrin levels, erythrocyte glutathione levels, and glutathione peroxidase activity were significantly decreased compared to those of controls. There was no significant difference in superoxide dismutase activity compared to controls. The results suggest that the antioxidant deficiency and excessive peroxide-mediated damage may appear in non-insulin dependent diabetes mellitus.     

Oxidant/antioxidant status in blood of patients with malignant breast tumour and benign breast disease

The aim of this study was to investigate the alterations in lipid peroxidation and antioxidant enzyme defences in the blood of patients with malignant breast tumour and benign breast disease. Forty patients with malignant breast tumour, 20 patients with benign breast disease and also 20 healthy control subjects were recruited for the study. Malondialdehyde levels in plasma and erythrocytes, and the activities of erythrocyte CuZn-superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase were measured. Malondialdehyde levels were higher in patients with both benign breast disease and malignant breast tumour compared with control subjects. The activities of all antioxidant enzymes were higher in patients with malignant breast tumour, while only glutathione peroxidase and CuZn-superoxide dismutase activities were higher in patients with benign breast disease. Except for glucose-6-phosphate dehydrogenase, the antioxidant enzymes studied correlated positively with the malondialdehyde levels in patients with malignant breast tumour. On the other hand, only glucose-6-phosphate dehydrogenase activity was increased by the level of malignancy. The activity increases in erythrocyte antioxidant enzymes may be a compensatory upregulation in response to increased oxidative stress especially in patients with malignant breast tumour.     

Oxidant-antioxidant imbalance in the erythrocytes of sporadic amyotrophic lateral sclerosis patients correlates with the progression of disease

Free radicals are implicated in numerous disease processes including motor neuron degeneration (MND). Antioxidant defense enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G-6-PDH) in the erythrocytes are capable of detoxifying reactive oxygen species produced endogenously or exogenously. In the present study, the extent of lipid peroxidation (LPO) and antioxidant defenses were evaluated in the erythrocytes of 20 sporadic amyotrophic lateral sclerosis (ALS) patients and 20 controls. We observed that lipid peroxidation in the erythrocytes of amyotrophic lateral sclerosis patients significantly increased with respect to controls (P<0.001). On the other hand, catalase activity was found to be significantly lower (P<0.001). The activities of glucose-6-phosphate dehydrogenase, glutathione reductase and glutathione levels were also found to be significantly reduced in ALS patients compared to healthy subjects (P<0.001, P<0.01 and P<0.01, respectively). It was further observed that lipid peroxidation started to increase and catalase, glutathione reductase, glucose-6-phosphate dehydrogenase enzyme activities and glutathione levels started to decrease as amyotrophic lateral sclerosis progressed from 6 to 24 months, suggesting a correlation between these parameters and duration of amyotrophic lateral sclerosis. This study confirms the involvement of oxidative stress during the progression of amyotrophic lateral sclerosis and the need to develop specific peripheral biomarkers.     

Acute lindane intoxication: A study on lindane tissue concentration and oxidative stress-related parameters in liver and erythrocytes

Treatment of rats with daily dosis of 20 mg of lindane/kg for 3 consecutive days led to the accumulation of the insecticide in several tissues, including erythrocytes and liver. Lindane did not alter the hematocrit and hemoglobin concentration but reduced methemogiobin levels by 17%. Red blood cells from controls and lindane-treated rats, exposed to t-butyl hydroperoxide, exhibited comparable rates of oxygen uptake and visible chemiluminescence, whereas the induction period that precedes oxygen uptake was significantly enhanced in the latter group. Lindane treatment did not modify the activity of erythrocyte glutathione peroxidase, glucose-6-phosphate dehydrogenase, catalase, and methemoglobin reductase, being the total content of glutathione and superoxide dismutase activity significantly increased. The liver from lindane-treated rats showed an enhanced microsomal pro-oxidant activity, evidenced by higher cytochrome P450 content and NADPH-cytochrome c reductase and NADPH oxidase activities. The higher enzyme activities led to an increased superoxide anion generation (adrenochrome formation) and lipid peroxidation (measured either by the production of thiobarbituric acid reactants and spontaneous visible chemiluminescence). Concomitantly, liver glutathione content and the activity of glutathione peroxidase-glutathione reductase couple were augmented by lindane treatment, without any change in superoxide dismutase activity, together with a reduction in that of catalase. Results suggest that lindane does not alter the prooxidant/antioxidant status of the erythrocyte in conditions of a significant cellular accumulation of the insecticide, which might exert direct action on enzymatic systems leading to enhanced superoxide dismutase activity and glutathione content. In the liver, lindane-induced pro-oxidant condition was not accompanied by cell injury, probably due to the adaptative increase in some antioxidant mechanisms of the hepatocyte.     

Impact of umbelliferone on erythrocyte redox status in STZ-diabetic rats

Oxidative stress is currently hypothesized to be a mechanism underlying diabetes. The present study was designed to evaluate the effect of umbelliferone (UMB), a derivative of coumarin, on erythrocyte lipid peroxidation, antioxidants, and lipid profile in normal and streptozotocin (STZ) diabetic rats. Diabetes was induced in adult male albino rats of Wistar strain, weighing 180 to 200 g, by the administration of STZ (40 mg/kg/b-wt) intraperitonially. The normal and diabetic rats were treated with UMB in 10 percent dimethyl sulfoxide (DMSO) dissolved in water for 45 days. The diabetic rats had elevated levels of blood glucose and lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD), and lipid hydroperoxide (HP) and decreased levels of nonenzymatic antioxidants (Vitamin C and reduced glutathione [GSH]), elevated levels of vitamin E, and elevated levels of enzymatic antioxidants (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx]), elevated glucose-6-phosphate dehydrogenase activity, and altered lipid profile (cholesterol and phospholipids) in erythrocytes. These changes were reversed by treatment with UMB. Thus, our results indicate that the administration of UMB shows promising potential for the restoration of normal blood glucose levels, erythrocyte lipid peroxidation, antioxidants, and lipid profile in STZ-diabetic.     

Effect of sodium nitrite poisoning on the activity of enzymes of anti-oxidant protection and peroxidation processes in mouse erythrocytes]

The intoxication of white mice with sodium nitrite results in the decrease of red cell superoxide dismutase (SOD) and catalase activity. The glutathione peroxidase activity is the same as in the control group. The level of red cell lipid peroxidation in the group of mice that receive sodium nitrite is higher as compared to the control group. After the intoxication the total activity of glucose-6-phosphate dehydrogenase and dehydrogenase of 6-phosphogluconate as well as the activity of glutathione reductase are higher than in the control group. The level of SH-groups and reduced glutathione is higher in the group of mice that receive sodium nitrite in comparison with the control group.     

Effect of diallyldisulphide on an antioxidant enzyme system in Candida species

This study was carried out to show the effect of diallyldisulphide (DADS), an important organosulphur compound found in garlic (Allium sativum), on antioxidant systems in Candida species. Changes in antioxidant metabolites and antioxidant activity in the presence of DADS were found in Candida albicans and Candida tropicalis. Candida cells were treated with sublethal concentrations of DADS. DADS caused a decrease in the activity of all antioxidant enzymes except catalase, resulting in oxidative stress and damaged cells. The amount of oxidative stress generated by DADS was found to be a function of its concentration. A significant decrease in superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase activities but an increase in catalase activity were observed. Increased levels of lipid peroxidation and decreased levels of glutathione were observed in treated cells. Activity of glucose-6-phosphate dehydrogenase decreased significantly following DADS treatment and could be correlated with a decrease in glutathione concentration in both Candida species. These results indicate that diallyl disulphide acts as a pro-oxidant to Candida species and hence may act as a potent antifungal in the management of candidiasis.     

Impact of chromium on lipoperoxidative processes and subsequent operation of the glutathione cycle in rat renal system.

Oral administration of K2Cr2O7 to male albino rats at an acute dose of 1500 mg/kg body wt/day for 3 days brought about sharp decrease in the activities of glucose-6-phosphate dehydrogenase and glutathione reductase of kidney epithelial cells. The scavenging system of kidney epithelium is also affected as evident by the highly significant fall in the activities of glutathione peroxidase, superoxide dismutase and catalase which ultimately leads to the increase in lipid peroxidation value in kidney cortical homogenate. However, glutathione-s-transferase activity in cytosol and glutathione and total thiol content in cortical homogenate were not altered. Chronic oral administration of K2Cr2O7 (300 mg/kg body wt/day) for 30 days to rats lead to elevation in the activities of glutathione peroxidase, glutathione reductase, glutathione-s-transferase, superoxide dismutase and catalase with no change in glucose-6-phosphate dehydrogenase activity in epithelial cells. This might lead to the increase in glutathione and total thiol status and decrease in lipid peroxidation value in whole homogenate system.     

Effect of radiotherapy and chemoradiotherapy on circulating antioxidant system of human uterine cervical carcinoma

Circulating lipid peroxide, antioxidant components and the activities of defense enzymes were estimated in uterine cervical carcinoma patients (before and after radiotherapy and radiotherapy combined chemotherapy) and compared with controls. Some of the antioxidant components such as glutathione, vitamin E and selenium are reduced in cervical cancer. The reduced levels of vitamin E and glutathione were normalized after treatment. Erythrocyte lipid peroxide (E-LPx) and erythrocyte membrane lipid peroxide (EM-LPx) levels were found to be increased in all the stages of uterine cervical carcinoma. The important antioxidant enzymes such as erythrocyte superoxide dismutase (E-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) were found to be decreased in uterine cervical carcinoma. These altered biochemical parameters were reversed to normal, of course with varied degree after different mode of therapy. Significant normalization was observed in Type 11 chemoradiotherapy.     

Effects of organophosphorus insecticide phosphomidon on antioxidant defence components of human erythrocyte and plasma.

Effect of organophosphorus insecticide, phosphomidon (250 and 500 ppm) on human erythrocyte and plasma were studied in vitro to get insight into the cellular antioxidant defence mechanism and malondialdehyde formation. The antioxidant defence system of erythrocyte was altered as evident by depression of glutathione reductase, glucose 6 phosphate dehydrogenase, whereas the level of reduced glutathione, glutathione peroxidase, glutathione-S-transferase, superoxidedismutase and catalase were stimulated. In the case of plasma fraction, glutathione reductase, glutathione peroxidase, glutathione-s-transferase, glucose-6-phosphate dehydrogenase, superoxide dismutase and levels of reduced glutathione were significantly depressed and the malondialdehyde formation and catalase activity were elevated indicating the less adaptive response of plasma to protect it from oxidative damage.     

The antioxidant status during maturation of reticulocytes to erythrocytes in type 2 diabetics

Free radical-induced lipid peroxidation has been associated with numerous disease processes including diabetes mellitus. The extent of lipid peroxidation (LPO) and antioxidant defense system [i.e., levels of glutathione (GSH), glucose-6-phosphate dehydrogenase (G6PDH), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), and catalase (CAT)] were evaluated in reticulocytes and erythrocytes of type 2 diabetic males and age-matched controls. Type 2 diabetics have shown increased lipid peroxidation and decreased levels of GSH, GR, GPx, G6PDH, and GST both in reticulocytes and erythrocytes compared to controls, indicating the presence of oxidative stress and defective antioxidant systems in these patients. CAT activity is found to be enhanced in both the reticulocytes and erythrocytes of diabetics, with a greater percentage enhancement in reticulocytes. The extent of increase in lipid peroxidation is greater in erythrocytes compared to reticulocytes in these patients. Furthermore, the maturation of reticulocytes to erythrocytes resulted in decreased GSH and decreased activities of all antioxidant enzymes (except CAT) both in normals and type 2 diabetes individuals, indicating decreased scavenging capacity as reticulocytes mature to erythrocytes. These maturational alterations are further intensified in type 2 diabetics. The present study reveals that the alterations in lipid peroxidation and antioxidant system lean toward early senescence of erythrocytes in type 2 diabetic patients.     

The effects of extracorporeal shock wave lithotripsy on antioxidant enzymes in erythrocytes

The effects of extracorporeal shock wave lithotripsy (ESWL) on patients undergoing ESWL for renal stone treatment have been studied using activities of glucose-6-phosphate dehydrogenase (G6PDH), superoxide dismutase (SOD) and catalase (CAT), and levels of malondialdehyde (MDA) in the erythrocyte haemolysate. The study included 23 patients (eight women, 15 men with an age range of 23-57 years). Blood samples were taken 5 min before ESWL, in addition to 1 h and 5 days after termination of treatment. Enzyme activities and MDA levels in erythrocytes were measured spectrophotometrically. When compared with the values obtained before ESWL, erythrocyte G6PDH (p = 0.015), SOD (p = 0.036) and CAT (p = 0.01) activities were found to be significantly reduced at the first hour after ESWL. On the fifth day after ESWL, erythrocyte enzyme activities were normalized to the values obtained before ESWL. Although there was a significant difference between values before and 1 h after ESWL (p = 0.003), no difference was detected between 1 h after ESWL and 5 days after ESWL (p > 0.05) in terms of MDA values. The findings of the present study revealed that erythrocyte lipid peroxidation might be induced and antioxidative defence mechanism may be transiently impaired by ESWL.     

Antioxidant Status in the Blood of Patients With Active Vitiligo

We have previously reported that patients with active vitiligo (AVP) have elevated urinary levels of catecholamine metabolites, such as homovanillic and vanilmandelic acids, irrespective of the form of the disease (acrofacial, segmental, generalized). We have suggested that abnormal release of catecholamines from autonomic nerve endings might play an etiological role in the onset and development of vitiligo through an overproduction of toxic (oxy)radicals in the microenvironment of melanocytes in the affected areas. In the present study we have investigated whether this suggested increase in radicals might be associated with an oxidative stress in the blood of AVP. We have analyzed by gas-chromatography mass-spectrometry, by high pressure liquid chromatography, by spectophotometry plasma levels of vitamin E (Vit E), lipoperoxides (LIP), and polyunsaturated fatty acids of phospholipids (PL-FA), erythrocyte reduced glutathione (GSH), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) activities in 62 patients affected with different forms of active vitiligo (acrofacial, segmental, generalized) and in 60 age-matched controls. Our results show that blood levels of Vit E, SOD, GSH, GSH-Px activity, LIP and PL-FA in AVP were not significantly different from those of healthy age matched controls, indicating that melanocyte damage in vitiligo is not linked with a generalized oxidative stress.     

Effects of dietary carbohydrate intake on antioxidant enzyme activity and copper status in the copper-deficient streptozotocin (STZ) diabetic rat

The aim of this study was to investigate how dietary lactose, compared with sucrose, in association with copper deficiency influences the antioxidant and copper status in the diabetic rat. Two groups of male rats (n = 12) were fed copper-deficient diets containing either 300 g/kg of sucrose or 300 g/kg of lactose in a pair-feeding regime for 35 days. Six rats from each group were injected with streptozotocin to induce diabetes. After a further 16 days the animals were killed and the liver, heart, and kidney removed for the measurement of copper levels and the activities of antioxidant and related enzymes. Diabetes resulted in higher hepatic and renal copper levels compared with controls. The copper content of the heart and kidney in diabetic rats consuming sucrose was also significantly higher than in those consuming lactose. Catalase activity in the liver, heart, and kidney was significantly increased in diabetic rats compared with controls. Hepatic glutathione S-transferase and glucose-6-phosphate dehydrogenase and cardiac copper zinc superoxide dismutase activities were also higher in diabetes. Sucrose, compared with lactose feeding, resulted in higher cytochrome c oxidase and glutathione peroxidase activities in the kidney while glucose-6-phosphate dehydrogenase activity was lower. The combination of lactose feeding and diabetes resulted in significantly higher activities of cardiac managanese superoxide dismutase and catalase and renal manganese superoxide dismutase and glucose-6-phosphate dehydrogenase. These results suggest that sucrose consumption compared with lactose appears to be associated with increased organ copper content and in general decreased antioxidant enzyme activities in copper-deficient diabetic rats.     

Activation of peroxisomal acyl-CoA oxidase and lipid peroxidation in the rat myocardium as affected by prolonged administration of ethanol

The influence of chronic alcoholic intoxication on the activity of peroxisomal acyl-CoA oxidase and antioxidative defensive enzymes (catalase, glutathione reductase, glutathione-S-transferase, superoxide dismutase, glucose-6-phosphate dehydrogenase) was studied in the rat myocardium. The parameters of lipid peroxidation in cardiomyocytes (the level of spontaneous chemiluminescence, accumulation of thiobarbituric acid-reactive material), as well as reduced glutathione content were also examined. The data obtained suggest that ethanol-induced activation of lipid peroxidation in the myocardium may be due to the elevation of hydrogen peroxide-generating activity of peroxisomes.     

The state of the antioxidant system during therapy of patients with multiple sclerosis

Activity of erythrocyte glutathione peroxidase (GPx), glutathione reductase (GR), glutathione transferase (GT), glucose-6-phosphate dehydrogenase (G6PDH), catalase and superoxide dismutase (SOD), the level of erythrocyte malonic dialdehyde (MDA) and also total antioxidant activity of blood serum were studied in patients with different types of multiple sclerosis (MS). Investigation of peripherical blood was carried out on the first day of admission to the hospital and after the standard therapy with copaxone. During the whole period of observation all MS patients had a high level of MDA and activity of erythrocyte GP compared with a control group. Other erythrocyte antioxidant enzymes and total antioxidant activity of blood serum exhibited weak positive dynamics in patients with relapsing-remitting multiple sclerosis (RRMS). The pathological decrease of antioxidant system activity in patients with secondary progressive multiple sclerosis (SPMS) was more pronounced and remained unchanged after the treatment. This is consistent with a more severe clinical course of this disease.     

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.     

Effect of chronic ethanol treatment under partial catalase inhibition on the activity of enzymes related to peroxide metabolism in rat liver and heart

1. In order to test the hypothesis that the alcoholic cardiomyopathy under partial catalase inhibition is associated with the activation of lipid peroxidation in cardiomyocytes (Panchenko et al., Experientia 43, 580-581, 1987), the effects of ethanol and catalase inhibitor 3-amino-1,2,4-triazole (aminotriazole) on rat heart and liver content of reduced glutathione and on the activity of enzymes related to peroxide metabolism: catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase and glucose-6-phosphate dehydrogenase were investigated. 2. In accordance with the data obtained by Kino (J. molec, cell. Cardiol. 13, 5-12, 1981), when ethanol (36% of dietary calories) and aminotriazole were simultaneously administered an alcoholic cardiomyopathy developed while in the liver moderate fatty degeneration was revealed. 3. Chronic combined or separate administration of ethanol and aminotriazole was shown to increase glutathione concentration and glutathione-S-transferase activity in rat liver. In the groups of animals which received isocaloric carbohydrates in the diet instead of ethanol the liver glucose-6-phosphate dehydrogenase was increased. 4. Acute and chronic aminotriazole injections led to catalase inactivation and in the latter case also to inhibition of the liver superoxide dismutase and glutathione peroxidase activities. 5. Ethanol and aminotriazole treatment did not alter the glutathione level and the activity of all enzymes tested (except catalase) in rat myocardium.     

Pro-oxidant and antioxidant processes in gas gland and other tissues of cod (Gadus morhua)

Partial reduction of molecular oxygen produces reactive oxyradicals, including the superoxide anion radical (O _- ² ) and hydroxyl radical (·OH). The gas gland functions under hyperoxic and acidic conditions and therefore is likely to be subjected to enhanced oxidative stress. Aspects of pro- and antioxidant processes in gas gland were compared with other tissues likely to be subject to differing degrees of oxyradical production, viz. liver (site of chemically-mediated oxyradical production), gills and skeletal muscle. Antioxidant enzyme activities (superoxide dismutase, catalase, selenium-dependent and total glutathione peroxidase) per g wet weight were highest in liver and lowest in muscle. Catalase and glutathione peroxidase activies per g wet weight were higher in gills than in gas gland, whereas the reverse was seen for superoxide dismutase. Cytosolic superoxide dismutase activities per mg protein were two- and nine-fold higher in gas gland than in liver and gills. The pH characteristics of the antioxidant enzymes were generally similar in all the tissues. Glutathione, vitamin E and unsaturated (peroxidizable) lipid levels were generally highest in liver followed by gas gland. Lipid peroxidation (malonaldehyde equivalents) was evident in all tissues except gas gland. Hydrogen peroxide and O _- ² were involved in the NAD(P)H-dependent ferric/EDTA-mediated formation of ·OH (as measured by 2-keto-4-methiolbutyrate oxidation) by mitochondrial and postmitochondrial fractions of gas gland. Tissue maximal potentials for ·OH production paralled superoxide dismutase but not catalase or glutathione peroxidase activities. Overall, the results confirm the presence of effective antioxidant defences in gas gland and support previous workers' contentions of a central role for superoxide dismutase in this process.Abbreviations EDTA di-sodium ethylenediaminetetra-acetic acid - G-6-P glucose-6-phosphate - GPX total glutathione peroxidase - GSH reduced glutathione - GSSG oxidised glutathione - GST glutathion-S-transferase - HPLC high performance liquid chromatography - KMBA 2-keto-4-methiolbutyric acid - MOPS 3-[N-morpholino] propane-sulphonic acid - PMS postmitochondrial supernatant - Se-GPX selenium-dependent glutathion peroxidase - SOD superoxide dismutase - TCA trichloroacetic acid     

Antioxidants and Manganese Deficiency in Needles of Norway Spruce (Picea abies L.) Trees

Chlorotic and green needles from Norway spruce (Picea abies L.) trees were sampled in the Calcareous Bavarian Alps in winter. The needles were used for analysis of the mineral and pigment contents, the levels of antioxidants (ascorbate, glutathione), and the activities of protective enzymes (superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate radical reductase, dehydroascorbate reductase, glutathione reductase). In addition, the activities of two respiratory enzymes (glucose-6-phosphate dehydrogenase, NAD-malate dehydrogenase), which might provide the NADPH necessary for functioning of the antioxidative system, were determined. We found that chlorotic needles were severely manganese deficient (3 to 6 micrograms Mn per gram dry weight as compared with up to 190 micrograms Mn per gram dry weight in green needles) but had a similar dry weight to fresh weight ratio, had a similar protein content, and showed no evidence for enhanced lipid peroxidation as compared with green needles. In chlorotic needles, the level of total ascorbate and the activities of superoxide dismutase, monodehydroascorbate radical reductase, NAD-malate dehydrogenase, and glucose-6-phosphate dehydrogenase were significantly increased, whereas the levels of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase, and glutathione were not affected. The ratio of ascorbate to dehydroascorbate was similar in both green and chlorotic needles. These results suggest that in spruce needles monodehydroascorbate radical reductase is the key enzyme involved in maintaining ascorbate in its reduced state. The reductant necessary for this process may have been supplied at the expense of photosynthate.