Purification and immunohistochemical tissue localization of human xanthine oxidase

Xanthine oxidase was purified 1600-fold from human liver cytosol. The purified enzyme was shown as a single band of 300 kDa on polyacrylamide gel electrophoresis and 150 kDa on SDS-PAGE. Using this purified enzyme, polyclonal antibody against xanthine oxidase was raised in a rabbit. On Ouchterlony's double immunodiffusion method, the raised antibody and the human liver cytosol made a precipitation line stained by activity stain and protein stain, respectively. With the raised anti-xanthine oxidase sera, the immunohistochemical localization of xanthine oxidase in human tissues was examined. Immunostaining of frozen hepatic tissue section showed that the cytoplasm of hepatocytes and endothelial lining cells were stained. In a number of other tissues, the xanthine oxidase antigen was detected only in the endothelial lining cells from heart, kidney, brain, aorta, lung and mesentery, except for the duodenal mucosa cells. A possible role for xanthine oxidase in the endothelial cells from various human tissues in the pathogenesis of reperfusion injury was suggested.