Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Xanthines”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1976

Subunit structure of bovine milk xanthine oxidase. Effect of limited cleavage by proteolytic enzymes on activity and structure.

Bovine milk xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) has been purified by a modified method without the use of proteases, and its structure has been analyzed by polyacrylamide gel electrophoresis. Native xanthine oxidase is found to consist of only two polypeptide chains A with molecular weights of 150 000 each. These chains have NH2-terminal methionine. Limited proteolysis with trypsin, chymotrypsin, or subtilisin at pH 8 did not affect molecular weight and activities of the enzyme while each of the A chains was cleaved under these conditions to three fragments C, E, and F with molecular weights of 92 00, 42 000 and 20 000, respectively. These fragments remained bound to each other and were relatively resistant to subsequent proteolysis. The isolation of xanthine oxidase in the presence of pancreatin as described by Hart et al. (1970, Biochem. J. 116, 851) gives partially digested enzyme composed mainly of chains C, E (Mr 35 000) and a small component (Mr approx. 15 0-0). The action of subtilisin on xanthine oxidase at pH 11 resulted in complete digestion of E chains, FAD separation, and total loss of xanthine:oxygen oxidoreductase activity while xanthine:indophenol oxidoreductase activity was relatively little affected. The residual enzyme has a molecular weight of about 200 000, is composed mainly of two C chains (and may probably contain F and/or proteolytic fragments of low molecular weight), contains molybdenum, and does not contain FAD.

Amino Acid Sequence↗
PubMed1986

Human and bovine xanthine oxidases. Inhibition studies with oxipurinol.

Oxipurinol inhibited human xanthine oxidase and bovine xanthine oxidases by very similar mechanisms. It bound to an electronically reduced form of human xanthine oxidase in a manner similar to that previously discerned from its interactions with the bovine enzyme [review article: Spector, Biochem. Pharmac. 26, 355 (1977)]. Xanthine was a good source for the reducing equivalents because it did not compete with oxipurinol for binding to reduced enzyme. The inhibition of the rate of urate production progressively increased with time. Studies of the effect of the concentration of oxipurinol on the rate constant of the development of this inhibition revealed that a complex was rapidly formed between oxipurinol and reduced bovine or human xanthine oxidases (KD of about 8 microM). At 37 degrees these complexes were converted to stable complexes at a maximum rate of about 1.6 min-1. The rate constant was highly temperature dependent with an energy of activation of 30 kcal/mole (cf. 13 kcal/mole for the energy of activation for catalysis). These data support the earlier conclusions that the formation of stable complexes probably reflects a massive rearrangement of the initial complexes. The isolated oxipurinol-xanthine oxidase complexes spontaneously reverted to active enzyme with a rate constant of 0.02 min-1 at 37 degrees. The energy of activation for the "reactivation" was similar to that for the formation of the stable complexes. The rates of "reactivation" could be stimulated by high concentrations of xanthine: 2.4-fold at 50 microM and 3.4-fold at 100 microM. The constant for the overall inhibition by oxipurinol was approximately 100 nM with both enzymes.

Animals↗
PubMed1989

Inhibition of xanthine oxidase by 4-hydroxy-6-mercaptopyrazolo[3,4-d]pyrimidine.

Compound B103U, 4-hydroxy-6-mercaptopyrazolo[3,4-d]pyrimidine, was investigated as an inhibitor of human xanthine oxidase. Studies in vitro demonstrated that it was significantly more potent than oxypurinol, 4,6-dihydroxypyrazolo[3,4-d]pyrimidine. It formed an initial complex with electron-rich (reduced) human xanthine oxidase that was tighter than the corresponding complex formed by oxypurinol. The initial complexes with each inhibitor and reduced enzyme were internally rearranged into more stable complexes with first-order rate constants of 2.5 to 3 per min. However, the half-life of the isomerized (stable) complex with B103U was three to four times longer than the half-life of the analogous complex with oxypurinol. This stability was previously noted by Massey et al. (J. Biol Chem 254: 2837-2844, 1970) with B103U and bovine xanthine oxidase. The overall Ki values accounting for the initial and isomerized complexes were 5 nM for B103U and 100 nM for oxypurinol. B103U was also more potent as an inhibitor of bovine xanthine oxidase-catalyzed generation of superoxide radicals. Studies in mice revealed that the relative in vitro potency of B103U was not sustained in vivo. Compared to the inhibition of xanthine oxidase by oxypurinol, inhibition by B103U was neither more potent nor longer lasting. This shortcoming was not caused by weaker inhibition of mouse xanthine oxidase. Instead, it was the result of poor bioavailability. Plasma levels of available B103U rapidly decreased from samples of mouse and human blood because of reversible binding to serum proteins. B103U was also susceptible to oxidation. Two equivalents of H2O2 stoichiometrically oxidized the 6-thiol substituent to a sulfinic acid. This oxidized product was three orders of magnitude weaker as an inhibitor of xanthine oxidase than was B103U.

Animals↗
PubMed1982

Differentiation between bronchodilation and universal adenosine antagonism among xanthine derivatives.

Relaxant effects and adenosine-antagonism of 3-propyl-xanthine (enprofylline) and 10 different methyl-xanthines were examined in isolated guinea-pig tracheas. The chemical structural requirements for tracheal relaxation were found to be different from those for adenosine antagonism by the xanthine derivatives. All xanthines produced relaxation: Enprofylline was about 5 times more potent than theophylline. However, only xanthines with a methyl in the 1-position consistently antagonized the relaxant effect of adenosine. --Theophylline over a wide range of concentrations (30-900 microM) produced a concentration dependent and surmountable antagonism at nervous adenosine receptors (isolated guinea-pig myenteric-plexus preparations). The same concentrations of enprofylline were almost devoid of antagonism at these adenosine receptors. In mice theophylline (6-24 mg/kg given intraperitoneally) dose-dependently increased locomotor activity while enprofylline (2-48 mg/Kg) was without effect on behaviour. "Non-blocking" xanthines such as enprofylline may be potent bronchodilators but lack many theophylline-like actions. We, therefore, forward the hypothesis that universal adenosine antagonism is both unnecessary and undesirable with xanthine antiasthmatics.

Adenosine↗
PubMed1983

Studies on the specificity toward aldehyde substrates and steady-state kinetics of xanthine oxidase.

The aldehyde specificity of xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) has been reinvestigated. The biogenic aldehydes and succinate semialdehyde are reasonable substrates for xanthine oxidase. Pyrophosphate, which binds to xanthine oxidase, does not seem to affect significantly the enzyme's catalytic activity. The steady-state parameters for the oxidation of several substrates by xanthine oxidase and oxygen have been determined. Formaldehyde differs from xanthine and other aldehydes in phi 2, the parameter describing the reaction with oxygen. Substrate inhibition has been studied at high concentrations of xanthine with oxygen as the electron acceptor. The inhibition is hyperbolic and uncompetitive with respect to oxygen. This is possibly due to rate-limiting product release from molybdenum(IV) being slower than from molybdenum(VI).

Aldehydes↗
PubMed2005

Synthesis and preliminary evaluation of new 1- and 3-[1-(2-hydroxy-3-phenoxypropyl)]xanthines from 2-amino-2-oxazolines as potential A1 and A2A adenosine receptor antagonists.

The development of potent and selective adenosine receptor ligands as potential drugs is an active area of research. Xanthines are one of the most important classes of adenosine receptor antagonists and have been widely developed in terms of affinity and selectivity for adenosine receptors. We recently developed new original pathways for the synthesis of xanthine analogues starting from 5-substituted-2-amino-2-oxazoline 5 as a synthon. These procedures allowed us to selectively introduce a large, functionalized and beta-adrenergic 2-hydroxy-3-phenoxypropyl pharmacophore at the 1- and 3-position of the xanthine moiety which allowed further structural modifications. In this study, we present a new synthetic access to racemic xanthine derivatives 1-4 from 5, and their evaluation as adenosine A1, A2A and A3 receptor ligands in radioligand binding studies. The 2-hydroxy-3-phenoxypropyl moiety was well tolerated in the 3-position of the xanthine core, while its introduction in the 1-position of the xanthine moiety led to a large decrease in adenosine receptor affinity. 1,7-Dimethyl-3-[1-(2-chloro-3-phenoxypropyl)]-8-(3,4,5-trimethoxystyryl)xanthine (2n) was the most potent and selective A2A antagonist of the present series (Ki=44 nM, >>200-fold selective vs A1). 1-Propyl-3-[1-(2-hydroxy-3-phenoxypropyl)]-8-noradamantylxanthine (3f) was identified as a potent (KiA1=21 nM) and highly selective (>>350-fold vs A2A and A3 receptor) adenosine A1 receptor antagonist.

Adenosine A1 Receptor Antagonists↗
PubMed2001

Marked elevation in cortical urate and xanthine oxidoreductase activity in experimental bacterial meningitis.

Experimental bacterial meningitis due to Streptococcus pneumoniae in infant rats was associated with a time-dependent increase in CSF and cortical urate that was approximately 30-fold elevated at 22 h after infection compared to baseline. This increase was mirrored by a 20-fold rise in cortical xanthine oxidoreductase activity. The relative proportion of the oxidant-producing xanthine oxidase to total activity did not increase, however. Blood plasma levels of urate also increased during infection, but part of this was as a consequence of dehydration, as reflected by elevated ascorbate concentrations in the plasma. Administration of the radical scavenger alpha-phenyl-tert-butyl nitrone, previously shown to be neuroprotective in the present model, did not significantly affect either xanthine dehydrogenase or xanthine oxidase activity, and increased even further cortical accumulation of urate. Treatment with the xanthine oxidoreductase inhibitor allopurinol inhibited CSF urate levels earlier than those in blood plasma, supporting the notion that urate was produced within the brain. However, this treatment did not prevent the loss of ascorbate and reduced glutathione in the cortex and CSF. Together with data from the literature, the results strongly suggest that xanthine oxidase is not a major cause of oxidative stress in bacterial meningitis and that urate formation due to induction of xanthine oxidoreductase in the brain may in fact represent a protective response.

Allopurinol↗
PubMed1988

Reperfusion-induced arrhythmias: a study of the role of xanthine oxidase-derived free radicals in the rat heart.

We have assessed whether oxygen-derived free radicals produced by xanthine oxidase may be an important trigger mechanism in the genesis of reperfusion-induced arrhythmias. We have examined (i) the effects of inhibition of xanthine oxidase by both folic acid solution and amflutizole; (ii) the effects of the inhibitor of xanthine dehydrogenase to xanthine oxidase conversion, soybean trypsin inhibitor; (iii) the effects of administration of superoxide dismutase and catalase, both singly and in combination and (iv) in an isolated rat heart preparation we have investigated the ability of free radical scavengers to reduce reperfusion arrhythmias caused by the infusion of xanthine oxidase and hypoxanthine. The prior administration of folic acid solution, amflutizole, superoxide dismutase, catalase, and superoxide dismutase plus catalase all reduced the incidence of reperfusion-induced arrhythmias and resultant mortality, caused by reperfusion after a transient period of coronary artery occlusion in the anaesthetised rat. Prior administration of soybean trypsin inhibitor significantly reduced mortality. In an isolated, perfused rat heart preparation with temporary coronary artery occlusion, addition of xanthine oxidase-hypoxanthine to the perfusion medium increased the incidence of reperfusion arrhythmias and decreased the total duration of sinus rhythm during reperfusion. Further addition of superoxide dismutase or L-methionine increased significantly the total duration of sinus rhythm. These results suggest that in the rat heart xanthine oxidase may be involved in the genesis of reperfusion-induced arrhythmias.

Allopurinol↗
PubMed1996

Histochemical study on xanthine oxidase activity in the normal rabbit cornea and lens and after repeated irradiation of the eye with UVB rays.

In the normal rabbit cornea and lens the activity of xanthine oxidase, an enzyme belonging to oxidases generating reactive oxygen species (ROS), is present in the corneal epithelium as well as endothelium and lens epithelium. Repeated irradiation of the eyes with UVB rays (5 min 1 x daily, for 1 to 4 days) caused a gradual increase of xanthine oxidase activity, particularly in the corneal epithelium. Application of catalase, a scavenger of hydrogen peroxide, to the eye surface during the irradiation diminished the increase of xanthine oxidase activity. On the contrary, the pretreatment of the rabbit eyes with 3-aminotriazole, an inhibitor of catalase, for 3 days before the irradiation enhanced the increase of xanthine oxidase activity. In comparison to untreated eyes, protracted irradiation of the eyes with UVB rays (up to 10 days) caused a decrease of xanthine oxidase activity in the same cell layers of the cornea and lens. It is suggested that xanthine oxidase is involved in the generation of ROS in the anterior eye segment during early irradiation of the eyes with UVB rays and participates in its damage. Prolonged repeated irradiation of the eye (5 min 1 x daily for 5 to 10 days) caused a decrease of xanthine oxidase activity in the cornea and lens which is attributed to profound damage of the whole anterior eye segment.

Amitrole↗
PubMed1987

Evidence for the existence of a tyrosyl residue in the nicotinamide adenine dinucleotide binding site of chicken liver xanthine dehydrogenase.

Xanthine-NAD and NADH-methylene blue oxidoreductase activities of chicken liver xanthine dehydrogenase were inactivated by incubation with 5'-[p-(fluorosulfonyl)benzoyl]adenosine (5'-FSBA), an active site directed reagent for nucleotide binding sites. The inactivation reaction displayed pseudo-first-order kinetics. A double-reciprocal plot of inactivation velocity vs. 5'-FSBA concentration showed that 5'-FSBA and enzyme formed a complex prior to inactivation. NAD protected the enzyme from inactivation by 5'-FSBA in a competitive fashion. The modified enzyme had the same xanthine-dichlorophenolindophenol and xanthine-O2 oxidoreductase activities as the native enzyme, and on addition of xanthine to the modified enzyme, bleaching of the spectrum occurred in the visible region. The amount of radioactivity incorporated into the enzyme by incubation with [14C]-5'-FSBA was parallel to the loss of xanthine-NAD oxidoreductase activity, and the stoichiometry was 1 mol/mol of enzyme-bound FAD for complete inactivation. These results indicated that 5'-FSBA modified specifically the binding site for NAD of chicken liver xanthine dehydrogenase. The incorporated radioactivity was released slowly from 14C-labeled enzyme by incubation with dithiothreitol with concomitant restoration of catalytic activity. The modified residue responsible for inactivation was identified as a tyrosine.

Animals↗
PubMed1997

Glutamate neurotoxicity in rat cerebellar granule cells: a major role for xanthine oxidase in oxygen radical formation.

To gain insight into the mechanism through which the neurotransmitter glutamate causally participates in several neurological diseases, in vitro cultured cerebellar granule cells were exposed to glutamate and oxygen radical production was investigated. To this aim, a novel procedure was developed to detect oxygen radicals; the fluorescent dye 2',7'-dichlorofluorescein was used to detect production of peroxides, and a specific search for the possible conversion of the enzyme xanthine dehydrogenase into xanthine oxidase after the excitotoxic glutamate pulse was undertaken. A 100 microM glutamate pulse administered to 7-day-old cerebellar granule cells is accompanied by the onset of neuronal death, the appearance of xanthine oxidase, and production of oxygen radicals. Xanthine oxidase activation and superoxide (O2.-) production are completely inhibited by concomitant incubation of glutamate with MK-801, a specific NMDA receptor antagonist, or by chelation of external calcium with EGTA. Partial inhibition of both cell death and parallel production of reactive oxygen species is achieved with allopurinol, a xanthine oxidase inhibitor, leupeptin, a protease inhibitor, reducing agents such as glutathione or dithiothreitol, antioxidants such as vitamin E and vitamin C, and externally added superoxide dismutase. It is concluded that glutamate-triggered, NMDA-mediated, massive Ca2+ influx induces rapid conversion of xanthine dehydrogenase into xanthine oxidase with subsequent production of reactive oxygen species that most probably have a causal involvement in the initial steps of the series of intracellular events leading to neuronal degeneration and death.

Animals↗
PubMed2004

Tandem orientation of duplicated xanthine dehydrogenase genes from Arabidopsis thaliana: differential gene expression and enzyme activities.

Xanthine dehydrogenase from the plant Arabidopsis thaliana was analyzed on molecular and biochemical levels. Whereas most other organisms appear to own only one gene for xanthine dehydrogenase A. thaliana possesses two genes in tandem orientation spaced by 704 base pairs. The cDNAs as well as the proteins AtXDH1 and AtXDH2 share an overall identity of 93% and show high homologies to xanthine dehydrogenases from other organisms. Whereas AtXDH2 mRNA is expressed constitutively, alterations of AtXDH1 transcript levels were observed at various stresses like drought, salinity, cold, and natural senescence, but also after abscisic acid treatment. Transcript alteration did not mandatorily result in changes of xanthine dehydrogenase activities. Whereas salt treatment had no effect on xanthine dehydrogenase activities, cold stress caused a decrease, but desiccation and senescence caused a strong increase of activities in leaves. Because AtXDH1 presumably is the more important isoenzyme in A. thaliana it was expressed in Pichia pastoris, purified, and used for biochemical studies. AtXDH1 protein is a homodimer of about 300 kDa consisting of identical subunits of 150 kDa. Like xanthine dehydrogenases from other organisms AtXDH1 uses hypoxanthine and xanthine as main substrates and is strongly inhibited by allopurinol. AtXDH1 could be activated by the purified molybdenum cofactor sulfurase ABA3 that converts inactive desulfo-into active sulfoenzymes. Finally it was found that AtXDH1 is a strict dehydrogenase and not an oxidase, but is able to produce superoxide radicals indicating that besides purine catabolism it might also be involved in response to various stresses that require reactive oxygen species.

Arabidopsis↗
PubMed1991

Allopurinol-insensitive oxygen radical formation by milk xanthine oxidase systems.

Oxygen radical generation in the xanthine- and NADH-oxygen reductase reactions by xanthine oxidase, was demonstrated using the ESR spin trap 5,5'-dimethyl-1- pyrroline-N-oxide. No xanthine-dependent oxygen radical formation was observed when allopurinol-treated xanthine oxidase was used. The significant superoxide generation in the NADH-oxygen reductase reaction by the enzyme was increased by the addition of menadione and adriamycin. The NADH-menadione and -adriamycin reductase activities of xanthine oxidase were assessed in terms of NADH oxidation. From Lineweaver-Burk plots, the Km and Vmax of xanthine oxidase were estimated to be respectively 51 microM and 5.5 s-1 for menadione and 12 microM and 0.4 s-1 for adriamycin. Allopurinol-inactivated xanthine oxidase generates superoxide and OH.radicals in the presence of NADH and menadione or adriamycin to the same extent as the native enzyme. Adriamycin radicals were observed when the reactions were carried out under an atmosphere of argon. The effects of superoxide dismutase and catalase revealed that OH.radicals were mainly generated through the direct reaction of H2O2 with semiquinoid forms of menadione and adriamycin.

Allopurinol↗
PubMed1996

Xanthine oxidase activity and free radical generation in patients with sepsis syndrome.

OBJECTIVE: To determine xanthine oxidase activity, free radical concentrations, and lipid peroxidation in patients with sepsis syndrome compared with noninfected critically ill patients. DESIGN: A prospective observational study. SETTING: A nine-bed intensive care unit in a university teaching hospital trust. PATIENTS: Fourteen consecutive patients who met the established criteria for sepsis syndrome with multiple organ dysfunction syndrome, and ten noninfected critically ill patients were studied. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Xanthine oxidase activity was increased in septic patients compared with both healthy volunteers (p < .01) and noninfected patients (p < .05), and was highest in the six patients who survived (p < .05). Lipid peroxides were increased in both septic patients (p < .001) and nonseptic controls (p < .001). Xanthine oxidase activity did not relate to the Acute Physiology and Chronic Health Evaluation (APACHE) II score or to the presence of organ dysfunction. The mean ascorbyl radical concentration (arbitrary units) determined by electron paramagnetic resonance following spin trapping was increased in patients compared with healthy subjects (p < .05). CONCLUSIONS: Patients with sepsis have xanthine oxidase activation, high free-radical concentrations, and evidence of free radical damage. The finding that xanthine oxidase activity was lower in those patients who died, coupled with increased lactate concentrations implies more severe ischemia with incomplete reperfusion resulting in less xanthine oxidase "wash out" into the circulation. Increased ascorbyl radical concentrations may be due to an increased radical generation and oxidant scavenging, but appears to be unrelated to xanthine oxidase activity within the circulation.

APACHE↗
PubMed1999

Amelioration of ischemia-reperfusion injury in rat intestine by pentoxifylline-mediated inhibition of xanthine oxidase.

BACKGROUND: Intestinal ischemia-reperfusion (IR) injury results in cell destruction, which may be mediated by the generation of reactive oxygen species, potentially toxic metabolites of xanthine oxidase. Pentoxifylline (PTX) possesses a variety of biochemical and antioxidant properties that can improve capillary flow and tissue oxygenation. Because of these combined effects, it has been hypothesized that pentoxifylline would protect against intestinal IR. METHODS: Young adult rats were randomly assigned to one of four experimental groups: IR/Placebo (n = 12) in which superior and inferior mesenteric arteries were clamped for 45 minutes and then reopened; IR/PTX (n = 11) in which IR was induced as in the Placebo group, but with 25 mg/kg PTX at 0, 30, and 60 minutes; No IR/Placebo (n = 12); and No IR/PTX (n = 6) in which placebo and PTX were applied with no IR. Blood and intestinal samples were taken for serial thiobarbituric acid-reducing substances (TBARS; index of lipid peroxidation), for xanthine oxidase-xanthine dehydrogenase ratios, glutathione, myeloperoxidase, and histopathology. RESULTS: Animals in the IR/PTX group had lower TBARS and the least severe histopathologic injury. Xanthine oxidasexanthine dehydrogenase ratios were elevated only in IR/ Placebo (0.67+/-0.22 vs. 0.45+/-0.14 in IR/PTX; 0.42+/-0.22 in No IR/Placebo; and 0.40+/-0.11 in No IR/PTX; p = 0.0009). Reduced glutathione was diminished in IR/PTX animals (38.9 +/-1.35 vs. 46.1+/-7.0 in IR/Placebo; 41.1+/-2.5 in No IR/ Placebo; 43.6+/-1.0 in No IR/PTX; p = 0.048). No differences were recorded in myeloperoxidase levels among groups. CONCLUSIONS: Pentoxifylline ameliorates histopathologic signs of injury and decreases lipid peroxidation (TBARS). Normal xanthine oxidase-xanthine dehydrogenase ratios in the treated compared with IR-only animals imply that the protective effect of PTX is at least partially mediated through inhibition of xanthine oxidase.

Animals↗
PubMed2001

Hepatic xanthine levels as viability predictor of livers procured from non-heart-beating donor pigs.

BACKGROUND: The aim of the present study was to evaluate hepatic content of adenine nucleotides and their degradation products in non-heart-beating donor (NHBD) pigs and its relationship with recipient survival. METHODS: Thirty animals were transplanted with an allograft from NHBDs. After warm ischemia (WI) time (20, 30, or 40 min), cardiopulmonary bypass and normothermic recirculation (NR) were run for 30 min. Afterward, the animals were cooled to 15 degrees C and liver procurement was performed. RESULTS: Survival rate was 100% in the 20WI, 70% in the 30WI, and 50% in the 40WI. Livers from non-surviving animals had higher levels of xanthine after NR than livers from surviving animals. Logistic regression analysis revealed that xanthine at the end of NR was the only variable able to predict survival with a calculated sensitivity of 80% and a specificity of 60%. Prolongation of warm ischemic period leaded to a greater xanthine accumulation as well as increased plasma alpha-glutathione S-transferase levels at reperfusion. Xanthine at NR and alpha-glutathione S-transferase at reperfusion significantly correlated, indicating that donor xanthine contributes to some extent to the severity of the lesion by ischemia-reperfusion. CONCLUSIONS: It is suggested that xanthine content in the donor is able to predict survival after transplantation. Xanthine is significantly involved in the hepatic lesion elicited by warm ischemia and subsequent ischemia-reperfusion associated to liver transplantation from a NHBD.

Animals↗
PubMed2003

Heparin mobilizes xanthine oxidase and induces lung inflammation in acute pancreatitis.

OBJECTIVE: To evaluate the effect of low molecular weight heparin on plasma xanthine oxidase concentrations and lung inflammatory response during acute pancreatitis. DESIGN: Randomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Acute pancreatitis was induced by intraductal administration of 5% sodium taurocholate. Low molecular weight heparin (0, 30, 90, or 300 units/kg) was administered immediately after induction of pancreatitis. MEASUREMENTS AND MAIN RESULTS: Lipase and xanthine oxidase plasma concentrations were measured 3 hrs after pancreatitis induction. Expression of P-selectin messenger RNA and myeloperoxidase activity as a marker of neutrophil infiltration were determined in the lung. An increase in xanthine oxidase plasma concentrations was observed during pancreatitis. Administration of heparin also increased plasma xanthine oxidase activity in both control and pancreatitis animals. Measures of xanthine oxidase present in the endothelial surface indicate that during pancreatitis, the enzyme is released from the gastrointestinal endothelium. By contrast, heparin mobilizes xanthine oxidase from almost all organs evaluated. Neutrophil infiltration was increased in the lung during pancreatitis. Heparin administration further increased, in a dose-dependent manner, myeloperoxidase activity and P-selectin expression in the lung in animals with pancreatitis. By contrast, in control animals, heparin had no effect on myeloperoxidase activity and did not induce P-selectin up-regulation. CONCLUSION: During acute pancreatitis, heparin administration might mobilize xanthine oxidase attached to endothelial cells, originating a free radical-generating system in the circulation that would trigger an inflammatory response in the lung.

Acute Disease↗
PubMed1993

Studies on the induction and phosphorylation of xanthine dehydrogenase in cultured chick embryo hepatocytes.

Chick embryo hepatocytes, cultured in a chemically defined medium, were used to investigate hormonal requirements for xanthine-dehydrogenase induction and to determine whether the enzyme is phosphorylated. Triiodothyronine is found to be required to induce the synthesis of active enzyme. Inclusion of sodium tungstate in the medium resulted in the complete loss of enzyme activity but no decrease of immunochemically detectable levels of enzyme. Immunoprecipitated xanthine dehydrogenase from cell extracts migrates with enzyme purified from adult chicken liver on SDS/PAGE. Both the native 150-kDa subunit and the 130-kDa form of the enzyme is observed. N-terminal sequence analysis of the 150-kDa subunit shows the following; Ala-Pro-Pro-Glu-Thr-Gly-Asp-Glu-Leu-Val-Phe-Phe-Val-Asn-Gly-Lys-Lys-Val- Val which is similar to the published N-terminal sequences of rat, mouse and insect xanthine dehydrogenases. Autoradiography of denaturing gels of xanthine dehydrogenase isolated from 32P(i)-labeled hepatocytes demonstrates that the 150-kDa and the 130-kDa forms of the enzyme are phosphorylated. Chemical phosphate analysis of acid-precipitated, electrophoretically pure chicken liver xanthine dehydrogenase also shows the presence of covalently bound phosphate. Phosphoamino acid analysis of both 32P-labeled forms of the enzyme demonstrates the presence of phosphoserine. Thus, chicken liver xanthine dehydrogenase contains a phosphoserine residue as found previously in bovine milk xanthine oxidase [Davis, M. D., Edmondson, D. E. & Müller, F. (1984) Eur. J. Biochem. 145, 237-250].

Amino Acid Sequence↗