Xanthine oxidase and superoxide radicals in portal triad crossclamping-induced microvascular reperfusion injury of the liver.
Although reactive oxygen metabolites may play a pivotal role in mediating microvascular reperfusion injury, the source of these radicals is still a matter of controversy. With the use of spectrophotometry and intravital microscopy we studied the role of xanthine oxidase and superoxide radicals in portal triad crossclamping-induced microvascular injury in rats. After 20 min of global hepatic ischemia and splanchnic vascular congestion, followed by 40 min of reperfusion (n = 8), xanthine oxidase activities in hepatic venous (26.9 +/- 4.7 nmol/ml x min) and systemic arterial blood (16.3 +/- 2.5 nmol/ml x min) were found significantly (p < .01) increased when compared with sham-operated controls (6.8 +/- 0.9 and 6.0 +/- 0.8 nmol/ml x min, n = 8). The increase of xanthine oxidase activity was accompanied by oxygen radical-mediated intravascular hemolysis. Intravital microscopy (n = 6) revealed accumulation of leukocytes within the postischemic hepatic microvasculature with stasis in sinusoids (75.9 +/- 8.9 per liver lobule) and adherence to the endothelial lining of postsinusoidal venules (534.7 +/- 125.3 per mm2 endothelial surface). Concomitantly, compromised microvascular reperfusion was characterized by perfusion deficits of individual sinusoids (25.6 +/- 4.0% nonperfused sinusoids). The xanthine oxidase inhibitor allopurinol (50 mg/kg b.wt., orally, n = 6) and the radical scavenger superoxide dismutase (60000 IU/kg b.wt., IV, n = 6) effectively (p < .01) inhibited both sinusoidal leukostasis (16.1 +/- 2.6 and 32.1 +/- 3.1 cells/lobule) and venular leukocyte adherence (247.6 +/- 7.9 and 205.0 +/- 38.0 cells/mm2), and, hence, reduced microcirculatory deteriorations, indicated by the attenuation of sinusoidal perfusion failure (2.8 +/- 0.8 and 9.0 +/- 3.1%). Our results support the hypothesis that portal triad crossclamping-induced microvascular reperfusion injury is triggered by superoxide radicals derived from the xanthine oxidase system.
Müller
M J
MJ
Institute for Clinical & Experimental Surgery, University of Saarland, Homburg/Saar, Germany.
Vollmar
B
B
Friedl
H P
HP
Menger
M D
MD
D000493:Allopurinol / Q000494:pharmacology; D000818:Animals; D003250:Constriction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals; D006461:Hemolysis; D006499:Hepatic Artery; D008099:Liver / Q000098:blood supply* / Q000201:enzymology; D008833:Microcirculation / Q000502:physiology; D011169:Portal Vein; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D005609:Free Radicals; D013481:Superoxides; D000493:Allopurinol; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase