The Relationship between Xanthine Oxidoreductase and Xanthine Oxidase Activities in Plasma and Kidney Dysfunction

Abstract

Background: Oxidative stress (OS) is thought to play a role in detrimental events among patients with chronic kidney disease (CKD). Although the mechanism of OS increases in CKD patients is unclear, it has been suggested that increased activity of xanthine oxidase (XO), the superoxide-producing form of xanthine oxidoreductase (XOR), plays a large role in enhancing OS. Therefore, we measured the activities of plasma XOR and XO among CKD patients. Methods: Thirteen CKD patients were enrolled in this study. Their plasma XOR and XO activities were measured using a liquid chromatography-triple quadrupole mass spectroscopy (LC-TQMS) method, and the ratio of XO to XOR (XO/XOR) was calculated. Results: The XOR and XO activities (pmol/h/mL plasma) were 8.30–58.2 and 9.15–40.8, and XO/XOR value was 0.698–1.240. Both XOR and XO showed positive correlation with estimated glomerular filtration rate (eGFR) (R=0.751, P=0.0020 and R=0.773, P=0.0031, respectively). On the other hand, XO/XOR showed negative correlation with eGFR (R=-0.614, P=0.0236). Conclusion: XOR and XO activities are decreased, and XO/XOR ratio is increased, in accordance with renal dysfunction. High XO/XOR ratio in advanced CKD patients might contribute to the elevation of OS.