In plasma samples, the following oxidative stress markers were measured: nitrite (NO2), superoxide anion radical (O2−), hydrogen peroxide (H2O2), and the index of lipid peroxidation (measured as TBARS – thiobarbituric acid reactive substances).
Nitric oxide decomposes rapidly to form stable metabolite nitrite/nitrate products. The nitrite level was measured and used as an index of nitric oxide (NO) production using the Griess reagent. A total of 0.5 ml of plasma was precipitated with 200 μl of 30% sulphosalicylic acid, vortexed for 30 min, and centrifuged at 3000 × g. Equal volumes of supernatant and Griess reagent containing 1% sulphanilamide in 5% phosphoric acid/0.1% naphthalene ethylenediamine dihydrochloride were added and incubated for 10 min in the dark, and the sample was measured at 543 nm. The nitrite levels were calculated using sodium nitrite as the standard [13 (link)].
The O2− concentration was measured after the reaction of nitro blue tetrazolium in Tris buffer with the plasma at 530 nm. Distilled water served as the blank [14 ].
The measurement of H2O2 is based on the oxidation of phenol red by H2O2 in a reaction catalysed by horseradish peroxidase (HRPO). Two hundred μl of plasma was precipitated with 800 ml of freshly prepared phenol red solution, followed by the addition of 10 μl of (1:20) HRPO (made ex tempore). Distilled water was used as the blank instead of the plasma sample. H2O2 was measured at 610 nm [15 (link)].
The degree of lipid peroxidation in the plasma samples was estimated by measuring TBARS using 1% thiobarbituric acid in 0.05 NaOH, incubated with the plasma at 100 °C for 15 min, and measured at 530 nm. Distilled water served as the blank [16 (link)].
The activity of the following antioxidants in the lysate was determined: reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). The level of reduced glutathione was determined based on GSH oxidation with 5,5-dithiobis-6,2-nitrobenzoic acid using a method by Beutler [17 ]. The CAT activity was determined according to Aebi [18 (link)]. The lysates were diluted with distilled water (1:7 v/v) and treated with chloroform-ethanol (0.6:1 v/v) to remove haemoglobin, and then 50 μl of CAT buffer, 100 μl of sample and 1 ml of 10 mM H2O2 were added to the samples. The detection was performed at 360 nm. SOD activity was determined by the epinephrine method of Beutler [19 (link)]. Lysate (100 μl) and 1 ml carbonate buffer were mixed, and then 100 μl of epinephrine was added. The detection was performed at 470 nm.
Nitric oxide decomposes rapidly to form stable metabolite nitrite/nitrate products. The nitrite level was measured and used as an index of nitric oxide (NO) production using the Griess reagent. A total of 0.5 ml of plasma was precipitated with 200 μl of 30% sulphosalicylic acid, vortexed for 30 min, and centrifuged at 3000 × g. Equal volumes of supernatant and Griess reagent containing 1% sulphanilamide in 5% phosphoric acid/0.1% naphthalene ethylenediamine dihydrochloride were added and incubated for 10 min in the dark, and the sample was measured at 543 nm. The nitrite levels were calculated using sodium nitrite as the standard [13 (link)].
The O2− concentration was measured after the reaction of nitro blue tetrazolium in Tris buffer with the plasma at 530 nm. Distilled water served as the blank [14 ].
The measurement of H2O2 is based on the oxidation of phenol red by H2O2 in a reaction catalysed by horseradish peroxidase (HRPO). Two hundred μl of plasma was precipitated with 800 ml of freshly prepared phenol red solution, followed by the addition of 10 μl of (1:20) HRPO (made ex tempore). Distilled water was used as the blank instead of the plasma sample. H2O2 was measured at 610 nm [15 (link)].
The degree of lipid peroxidation in the plasma samples was estimated by measuring TBARS using 1% thiobarbituric acid in 0.05 NaOH, incubated with the plasma at 100 °C for 15 min, and measured at 530 nm. Distilled water served as the blank [16 (link)].
The activity of the following antioxidants in the lysate was determined: reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). The level of reduced glutathione was determined based on GSH oxidation with 5,5-dithiobis-6,2-nitrobenzoic acid using a method by Beutler [17 ]. The CAT activity was determined according to Aebi [18 (link)]. The lysates were diluted with distilled water (1:7 v/v) and treated with chloroform-ethanol (0.6:1 v/v) to remove haemoglobin, and then 50 μl of CAT buffer, 100 μl of sample and 1 ml of 10 mM H2O2 were added to the samples. The detection was performed at 360 nm. SOD activity was determined by the epinephrine method of Beutler [19 (link)]. Lysate (100 μl) and 1 ml carbonate buffer were mixed, and then 100 μl of epinephrine was added. The detection was performed at 470 nm.
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