Changes In Antioxidant Levels Research Articles

Changes in antioxidant levels and activities of related enzymes in rice leaves exposed to ozone

Abstract Changes in the levels of antioxidants such as ascorbate and glutathione and activities of related enzymes in rice leaves exposed to ozone at high or low concentrations were investigated. In rice plants (Oryza sativa L. cv. Koshihikari) exposed to ozone at a high concentration (0.50 × 10-6 m3 m-3 (0.50 ppm)) for 8 h, L-ascorbate was oxidized while the content of oxidized glutathione (GSSG) increased without the concomitant decrease of the content of reduced glutathione (GSH). In addition, the activities of ascorbate peroxidase (AP), dehydroascorbate reductase (DHA reductase), and Superoxide dismutase (SOD) declined, though the glutathione reductase (GR) activity remained unchanged. A high concentration of ozone was considered to destroy the protection system against active oxygen species, resulting in the injury of the cell structure and functions. On the other hand, in the rice leaves exposed for 5 weeks to ozone at low concentrations (0.05 × 10-6 and 0.10 × 10-6 m3 m-3), the amount of L-ascorbate and total ascorbate increased significantly by exposure to 0.05 × 10-6 m3 m-3 O3 while the content of total glutathione (GSH + GSSG) decreased by exposure to 0.10 × 10-6 m3 m-3 O3. Activities of AP, GR, and SOD increased by the exposure to ozone at low concentrations. These reactions may be interpreted as protective responses to prevent or alleviate the damage of rice plants induced by ozone.

Seasonal changes in antioxidants in red spruce (Picea rubens Sarg.) from three field sites in the northeastern United States.

Changes in antioxidant levels were investigated in red spruce (Picea rubens Sarg.) from three field sites in the northeastern United States. Whiteface Mountain, NY at an elevation of 1090 m, represents a red spruce population in decline, while Millinocket and Howland, Maine are at 518 and 105 m above sea level, respectively, and have red spruce stands that show no symptoms of decline. The Millinocket site with saplings that are 15-20 yr old was compared with the Howland site with 60-yr-old trees to test the effect of age on antioxidant levels. The Howland site was compared with the Whiteface Mountain site, which has trees more than 100 yr old, to test the effects of air quality and elevation. Foliage developed in 1987 (87 needles) and in 1988 (88 needles) was sampled from May to November and from July to November, 1988, respectively. Quadratic polynomial and linear regressions were used to model the relationships through time of each variable measured. Regression coefficients were obtained by one-way analysis of variance. The means for total glutathione and oxidized glutathione were higher at Whiteface Mountain in 87 needles, and needles of both age classes sampled in November had significantly higher oxidized glutathione at Whiteface Mountain compared to those at Howland. No significant difference was observed in the mean ascorbate content of either needle class at all the three sites. The activity of superoxide dismutase declined with time in 87 needles at Whiteface Mountain and the mean activity was lower at Whiteface Mountain than at Howland. The effects of ozone concentration, site elevation and other environmental factors on seasonal changes in antioxidant levels and superoxide dismutase activity are discussed.

Relationship between foliar injury and changes in antioxidant levels in red and Norway spruce exposed to acidic mists

Elevated levels of total glutathione and enhanced activities of glutathione reductase and ascorbate peroxidase were found in needles of red spruce which had been exposed to acidic mists. Reduced levels of ascorbate were also detected. Such observations suggest that oxidative stress is involved in processes which resist foliar injury caused by acidic misting. Different ionic compositions of the acidic mists applied had pronounced effects on the levels of these antioxidants and the activities of related enzymes. Sulphate was found to be most effective in causing increases in glutathione, while additions of ammonium and/or nitrate mitigated the effects of sulphuric acid. Moreover, it is the composition of ions in the applied mists, rather than the levels of acidity, that determines the extent of the overall response of red spruce. By contrast, although acidic mists caused similar increases in glutathione content of Norway spruce needles, no statistically significant changes of ascorbate or related enzymic activities were found.

Changes in antioxidant levels, catecholamines and β-adrenoceptor function in the rat by physical and emotional stress

Changes in antioxidant levels, catecholamines and β-adrenoceptor function in the rat by physical and emotional stress

Effects of culture duration on hydrogen peroxide-induced hepatocyte toxicity

The effects of culture duration on primary cultured mouse hepatocyte antioxidant levels (superoxide dismutase, catalase, glutathione peroxidase, vitamin E, and glutathione) and susceptibility to glucose oxidase (GO)- and hydrogen peroxide (H 2O 2)-induced cell killing and lipid peroxidation were examined. Membrane fatty acid composition was also evaluated. Adult male B6C3F1/CrlBR mouse hepatocytes were isolated by collagenase perfusion of the liver and cultured on 60-mm plastic dishes in Leibovitz's L-15 medium supplemented with glucose (1 mg/ml), dexamethasone (1 μ m), fetal bovine serum (10%, v/v), and gentamicin sulfate (50 μg/ml) for 0 hr (freshly isolated cells) to 96 hr. Hepatocyte toxicity (determined by lactate dehydrogenase release and lipid peroxidation) after a 2-hr exposure to GO (0.8–80 μg/ml) or H 2O 2 (1–5 m m) decreased with increased time in culture. This decreased hepatocyte sensitivity to GO and H 2O 2 toxicity was not related to antioxidant enzyme activity since superoxide dismutase, catalase, and glutathione peroxidase declined during the 96-hr culture period. In contrast, glutathione and vitamin E levels in the cultured hepatocytes rose to 274.9 ± 8.3% and 220.6 ± 18.6% of the levels in freshly isolated cells (129.6 ± 11.5 nmol and 0.10 ± 0.01 nmol per 10 6 hepatocytes, respectively). The percentage of polyunsaturated fatty acids in hepatocyte phospholipids and triglycerides decreased with culture duration while the percentage of oleic acid increased in esterified and free fatty acid pools after 2 hr in culture. Total fatty acids were not affected by time in culture. These results suggest that the decreased hepatocyte susceptibility to the toxic effects of hydrogen peroxide may have been due to elevations in cellular GSH and vitamin E levels and decreases in membrane polyunsaturated fatty acids. The data also indicate that hepatocytes in primary culture undergo changes in antioxidant levels and fatty acid composition that may affect free radical toxicity at different times in culture.