Xanthine oxidase (XO) activity was found to be negligible in sterile human urines (less than 480 units, as presently defined, per litre). Significant XO activity was found in all urines containing more than 10(5) bacteria/ml, except for urines infected with Staphylococcus aureus, in which XO activity ranged from 347 to 714 units per litre. Plasma XO is not transferred to the urine, as demonstra...

Concentrations of up to 1.5 milliunits/ml xanthine oxidase (XO) (1.1 micrograms/ml) are found circulating in plasma during diverse inflammatory events. The saturable, high affinity binding of extracellular XO to vascular endothelium and the effects of cell binding on both XO catalytic activity and differentiated vascular cell function are reported herein. Xanthine oxidase purified from bovine c...

BACKGROUND Acrylonitrile (ACN) is an extensively produced aliphatic nitrile. The gastrointestinal tract is an important target organ for ACN toxicity. The objective of the present study was to investigate the role of xanthine oxidase (XO) in ACN-induced gastric toxicity in rats. MATERIAL/METHODS We assessed the effect of ACN on oxidative stress parameters as xanthine oxidase (XO) and total xa...

Xanthine oxidase (XO), a key enzyme in purine metabolism, produces reactive oxygen species causing vascular injuries and chronic heart failure. Here, copper's ability to alter XO activity and structure was investigated in vitro after pre-incubation of the enzyme with increasing Cu(2+) concentrations for various periods of time. The enzymatic activity was measured by following XO-catalyzed xanth...

Hypoxia increases the activity of xanthine oxidase (XO) and its precursor, xanthine dehydrogenase (XDH), but the mechanism of regulation is unclear. In hypoxic Swiss 3T3 cells, an early (0-24 h) cycloheximide-insensitive increase in XO-XDH activity, coupled with a lack of increase in de novo XO-XDH synthesis (immunoprecipitation) or mRNA levels (quantitative RT-PCR), demonstrated a posttranslat...

Circulating xanthine oxidase (XO) can modify adhesive interactions between neutrophils and the vascular endothelium, although the mechanism underlying this effect are not clear. We found that treatment with XO of bovine pulmonary artery endothelial cells (EC), but not neutrophils or plasma, increased adherence, suggesting that XO had its primary effect on EC. The mechanism by which XO increased...

We measured time course and extent of xanthine dehydrogenase (XD) to xanthine oxidase (XO) conversion in ischemic human and rat intestine. To model normothermic no-flow ischemia, we incubated fresh biopsies for 0, 2, 4, 8 and 16h. At t = 0h, XO was less in humans than in rats (P < 0.0004), while XD was essentially the same (P = NS). After 16h incubation at 37 degrees C, there was no appreciable...

Xanthine oxidase (XO) has been recognized as an important host defense enzyme for decades. In our recent study in Infection and Immunity, we found that enteropathogenic and Shiga-toxigenic E. coli (EPEC and STEC) were far more resistant to killing by the XO pathway than laboratory E. coli strains used in the past. Although XO plus hypoxanthine substrate rarely generated enough H 2O 2 to kill EP...