The role of xanthine oxidase in platelet activating factor induced intestinal injury in the rat.
BACKGROUND
Xanthine oxidase (XO) is an important source of reactive oxygen species in the small intestine.


OBJECTIVE
To examine the interaction of platelet activating factor (PAF), XO, and neutrophils in mediating intestinal injury in rats.


METHODS
Two doses of PAF were used to induce either reversible hypotension, or irreversible shock with intestinal necrosis. The activities of XO, and its precursor xanthine dehydrogenase (XD), in both the whole intestinal tissue and epithelial cells, were measured. XO was localised by histochemical staining.


RESULTS
PAF dose dependently induced an increase in XO activity, predominantly in the ileal epithelium, without altering the total activity of XD+XO. Most of the XD to XO conversion was via proteolysis. PAF induced XO activation and intestinal injury were prevented by prior neutrophil depletion. PAF induced XO activation is probably not due to reperfusion, as XO activation preceded the recovery of mesenteric flow. Allopurinol pretreatment substantially inhibited intestinal neutrophil sequestration induced by high dose (but not low dose) PAF.


CONCLUSIONS
PAF rapidly activates intestinal XO through proteolytic XD-XO conversion, predominantly in the ileal epithelium. This effect is mediated by neutrophils. XO activation promotes PAF induced polymorphonuclear leucocyte sequestration in the intestine.
Qu
X W
XW
Department of Pathology, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, USA.
Rozenfeld
R A
RA
Huang
W
W
Bulkley
G B
GB
Hsueh
W
W
D000493:Allopurinol / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000201:enzymology; D007082:Ileum / Q000201:enzymology* / Q000473:pathology*; D008297:Male; D009336:Necrosis; D010972:Platelet Activating Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014968:Xanthine Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010972:Platelet Activating Factor; D000493:Allopurinol; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase