Determination of glutathione reductase activity and oxidized/reduced glutathione ratio in colon cancer patients

Colon cancer (CC) is the third leading cause of cancer-related mortality worldwide. Given the role of oxidative stress in carcinogenesis, this study investigated glutathione reductase (GR; EC 1.8.1.7) activity and oxidative stress markers, including reduced glutathione (GSH), oxidized glutathione (GSSG), and the GSH/GSSG ratio, in the etiopathogenesis of CC. Erythrocytes were isolated from 3 mL blood samples collected from volunteers aged 18–75 years. Hemoglobin concentration was determined spectrophotometrically at 540 nm by monitoring the conversion of methemoglobin to cyanmethemoglobin in the presence of cyanide. GR activity was measured at 340 nm by monitoring Reduced Nicotinamide Adenine Dinucleotide Phosphate (NADPH+H+) oxidation, whereas GSH and GSSG levels were determined at 412 nm based on the formation of 2-nitro-5-thiobenzoic acid. In patients with CC, GR activity was 1.41 ± 0.39 U/gHb, GSH concentration was 6.96 ± 1.45 nmol/gHb, and the GSH/GSSG ratio was 1.04 ± 0.49. In healthy individuals, the corresponding values were 0.86 ± 0.18 U/gHb, 11.43 ± 1.90 nmol/gHb, and 3.86 ± 1.30. Statistical comparison revealed significantly lower GSH levels and significantly higher GR activity and GSSG levels in CC patients, indicating elevated oxidative stress. These findings suggest that GR activity and the GSH/GSSG ratio may serve as useful biomarkers for CC diagnosis and prognosis overall.observed. This indicates that oxidative stress levels are significantly elevated in cancer patients.