In studying the oxidation of xanthine manometrically by using liver homogenate systems (l), certain irregularities in the method have become evident to the authors. Occasionally an oxygen consumption has been observed after 2 to 3 hours of incubation which is greatly in excess of the theoretical requirement for the complete oxidation of the xanthine substrate. In certain experiments the measure...

The influence of dietary protein on the activity of rat liver xanthine oxidase has been studied by several workers (l-5) and would point to a relationship between the availability of amino acids and the activity of liver xanthine oxidase (2). It has been demonstrated that the loss of liver xanthine oxidase activity in the rat greatly exceeds the loss of liver protein during acute inanition (l),...

Lipofuscin was produced when HT29, a colon carcinoma cell line, was cultured in millimolar concentrations of xanthine and guanine but not in the presence of other bases. Using a simple assay developed to quantify the fluorescent pigment, it was found that maximum levels of lipofuscin were developed in 3 days. Methylxanthines that are not substrates of xanthine dehydrogenase, such as caffeine an...

The 13C-Nuclear Magnetic Resonance spectra of xanthine, 1,3-dimethyl-xanthine (theophylline), 3,7-dimethyl xanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) were obtained and the lines assigned. Protonationand N-Methylation parameters are derived by comparison of the 13C-chemical shifts of the protonated cations with those of the neutral molecules and also with those of the xanthine...

Xanthine oxidase activity containing fractions from rat, mouse, rabbit and guinea pig livers were obtained by heat treatment and ammonium sulfate precipitation. Xanthine oxidase activity was observed in rat and mouse liver fractions, while xanthine oxidase activity was absent in rabbit and guinea pig liver fractions. Enzyme kinetic parameters, K m and V max , were determined for the conversion ...

Xanthine oxidase (EC 1.2.3.2) activity increases in liver of rabbits deficient in vitamin E. Immunochemical titration of the enzyme demonstrates that the elevation of activity is due to an increased accumulation of the enzyme protein rather than activation of preexisting enzyme molecules. Immunochemically, xanthine oxidase from deficient animals is indistinguishable from the enzyme from control...

Oxygen metabolites have been implicated in the pathogenesis of various types of acute tissue injury. One biologic source of oxygen metabolites is the reaction catalyzed by the enzyme xanthine oxidase. Because we previously demonstrated that the substrates for xanthine oxidase (hypoxanthine and xanthine) are elevated in the plasma of critically il l patients, we questioned whether the enzyme its...

The enzyme xanthine oxidase has been implicated as a generator of toxic oxygen metabolites that contribute to ischemic injury. Because substantial species variability has been demonstrated and because there are minimal human data available, the relevance of xanthine oxidase to human heart damage has been in doubt. We report the absence of xanthine oxidase activity in nine human heart biopsy spe...

This study was designed to study xanthine oxidase (XO) and xanthine dehydrogenase (XD) activity in the lung of rats exposed to prolonged restraining immobilization stress. Immobilization caused more than twofold increase of xanthine oxidase activity in the rat lung. The activity of xanthine oxidase decreased in lung homogenates incubated at -20 degrees C for 24 h. The same incubation of homogen...

Passive Heymann nephritis (PHN) in rats is a model of human membranous nephropathy characterized by formation of subepithelial immune deposits in the glomerular capillary wall and complement activation. Oxygen radicals have been implicated in the subsequent glomerular damage which leads to proteinuria. This study examines the involvement of xanthine oxidase in this process. Xanthine oxidase act...