CIRCULATING XANTHINE-OXIDASE IN HUMAN ISCHEMIA-REPERFUSION

Reactive oxygen species (ROS) generated from xanthine oxidase (XO) play an important role in ischemia-induced injury. We hypothesize that XO and xanthine dehydrogenase (XDH) are released into the circulation with ischemia reperfusion to the human liver and intestine. Blood was drawn from a patient, before and at intervals after an aortic cross-clamp procedure. Plasma was incubated in the presence of xanthine, with NAD(+) (for XDH+XO) and without NAD(+) (for XO). The amount of mate formed was quantified using a high-performance liquid chromatograph (HPLC). The calculated XDH+XO and XO activity increased from 1.88 and 1.66 mu U/mg protein, respectively, before the cross clamp to 3.77 and 3.11 mu U/mg, respectively, 7 minutes after reperfusion to the superior mesenteric, celiac, and right renal artery beds. The release of a significant biological source of ROS may explain the damage to lung or heart observed after ischemia to the human liver and intestine.