Lactobacillus casei combined with Lactobacillus reuteri alleviate pancreatic cancer by inhibiting TLR4 to promote macrophage M1 polarization and regulate gut microbial homeostasis.

BACKGROUND: Pancreatic cancer is a highly lethal disease with no effective treatments. Lactobacillus casei (L. casei) and Lactobacillus reuteri (L. reuteri) exhibited therapeutic effects on several cancers, but their roles in pancreatic cancer are unknown. This study aims to explore how L. casei & L. reuteri influence pancreatic cancer and the underlying mechanisms. METHODS: Pancreatic cancer cells were treated with L. casei & L. reuteri and co-cultured with macrophages in a transwell system in vitro. Pancreatic cancer xenograft model was established and L. casei & L. reuteri was used to treat mice in vivo. MTT, CCK-8 assay or immunohistochemical staining were used to determine the proliferation of pancreatic cancer cells or tumor tissues. Transwell assay was applied to test the migration and invasion of pancreatic cells. RT-qPCR was utilized to assess TLR4 and MyD88 expressions in pancreatic cells or tumor tissues. WB, immunofluorescence staining, or flow cytometry was used to evaluate the M1/M2 polarization of macrophages. Besides, the composition of gut microbiota of tumor-bearing mice was determined by 16 S rRNA sequencing, and ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) untargeted metabolomics was used to evaluate the metabolic profiles of feces. RESULTS: L. casei & L. reuteri inhibited the proliferation, migration, invasion of pancreatic cancer cells and pancreatic cancer cell-induced M2 polarization of macrophages by suppressing TLR4. Meanwhile, L. casei & L. reuteri repressed pancreatic cancer growth and promoted M1 macrophage polarization. Besides, L. casei & L. reuteri reduced fecal Alloprevotella and increased fecal azelate and glutamate in nude mice, while TLR4 inhibitor TAK-242 increased Clostridia UCG-014, azelate, uridine, methionine sulfoxide, oxypurinol, and decreased glyceryl monoester in the feces of pancreatic tumor-bearing mice. Fecal oxypurinol and glyceryl monoester levels were positively or negatively associated with gut Clostridia UCG-014 abundance, respectively. CONCLUSION: L. casei & L. reuteri alleviate pancreatic cancer by inhibiting TLR4 to promote macrophage M1 polarization and regulate gut microbial homeostasis.

An association study of ABCG2 rs2231142 on the concentrations of allopurinol and its metabolites.

ABCG2 is a gene that codes for the human breast cancer resistance protein (BCRP). It is established that rs2231142 G>T, a single nucleotide polymorphism of the ABCG2 gene, is associated with gout and poor response to allopurinol, a uric acid-lowering agent used to treat this condition. It has also been suggested that oxypurinol, the primary active metabolite of allopurinol, is a substrate of the BCRP. We thus hypothesized that carrying the rs2231142 variant would be associated with decreased oxypurinol concentrations, which would explain the lower reduction in uric acid. We performed a cross-sectional study to investigate the association between the ABCG2 rs2231142 variant and oxypurinol, allopurinol, and allopurinol riboside concentrations in 459 participants from the Montreal Heart Institute Hospital Cohort. Age, sex, weight, use of diuretics, and estimated glomerular filtration rate were all significantly associated with oxypurinol plasma concentration. No association was found between rs2231142 and oxypurinol, allopurinol and allopurinol riboside plasma concentrations. Rs2231142 was not significantly associated with daily allopurinol dose in the overall population, but an association was observed in men, with T carriers receiving higher doses. Our results do not support a major role of ABCG2 in the pharmacokinetics of allopurinol or its metabolites. The underlying mechanism of the association between rs2231142 and allopurinol efficacy requires further investigation.

Relationships Between Allopurinol Dose, Oxypurinol Concentration and Urate-Lowering Response-In Search of a Minimum Effective Oxypurinol Concentration.

The aims of this study were to determine factors that predict serum urate (SU) lowering response to allopurinol and the conversion of allopurinol to oxypurinol, and to determine a minimum therapeutic oxypurinol concentration. Data from 129 participants in a 24-month open, randomized, controlled, parallel-group, comparative clinical trial were analyzed. Allopurinol dose, SU, and plasma oxypurinol concentrations were available at multiple time points. The slope for the association between allopurinol dose and SU was calculated as a measure of sensitivity to allopurinol. The slope for the association between allopurinol dose and oxypurinol was calculated as a measure of allopurinol metabolism. Receiver operating characteristic (ROC) curves were used to identify a minimum oxypurinol concentration predictive of SU < 6 mg/dL. There was a wide range of SU concentrations for each allopurinol dose. The relationship between sensitivity to allopurinol and allopurinol metabolism for each 100 mg allopurinol dose increase varied between individuals. Body mass index (P = 0.023), creatinine clearance (CrCL; P = 0.037), ABCG2 Q141K (P = 0.019), and SU (P = 0.004) were associated with sensitivity to allopurinol. The minimum oxypurinol concentration for achieving the urate target was found to be about 104 µmol/L, but predictive accuracy was poor (ROC curve area under the curve (AUC) 0.65). The minimum therapeutic oxypurinol concentration was found to increase with decreasing renal function. Although there is a positive relationship between change in oxypurinol and change in SU concentration, a minimum therapeutic oxypurinol is dependent on CrCL and cannot reliably predict SU target. Other variables, including ABCG2 Q141K genotype, impact on sensitivity to allopurinol (ACTRN12611000845932).

Uric acid analogue as a possible xenobiotic marker of uric acid transporter Urat1 in rats.

The inhibitor of uric acid reabsorptive transporter URAT1 in kidney is drawing attention as a drug target for hyperuricemia. However, it is difficult to evaluate efficacy of URAT1 inhibitors in vivo using laboratory animals due to species difference in uric acid metabolism. In the present study, the usefulness of exogenously administering uric acid analogues resistant to uricase was investigated for in vivo evaluation of transport activity of rUrat1 in rats. Uptake of examined four uric acid analogues by rUrat1-expressing Xenopus oocytes was significantly higher than that by water-injected oocytes. In metabolism studies, disappearance of these compounds was negligible, while uric acid was significantly decreased. When oxypurinol was administered to rats, fractional excretion (FE) was 0.4, suggesting reabsorption of oxypurinol. Moreover, FE of oxypurinol was tended to be increased, but not statistically different, by co-administration of a uricosuric agent FYU-981, while plasma concentration of oxypurinol was not affected. These results suggested that oxypurinol is a potential uric acid analogue, although it was not suitable as a probe of uric acid in in vivo study. Our findings may contribute to discovery and development of novel uricosuric agent targeting URAT1.

Pharmacokinetics, Pharmacodynamics, and Tolerability of Concomitant Multiple Dose Administration of Verinurad (RDEA3170) and Allopurinol in Adult Male Subjects With Gout.

Verinurad (RDEA3170) is a selective uric acid reabsorption inhibitor in clinical development for treatment of hyperuricemia and gout. This phase 1b, multiple-dose, drug-drug interaction study evaluated the pharmacokinetics, pharmacodynamics, and tolerability of verinurad in combination with allopurinol. Adult males with gout were randomized to receive once-daily oral doses of allopurinol 300 mg or verinurad 10 mg alone for 7 days, allopurinol 300 mg + verinurad 10 mg on days 8 to 14, and the alternative single agent on days 15 to 21. Colchicine 0.6 mg was taken prophylactically for gout flares. Plasma/serum and urine samples were assayed for verinurad, allopurinol, oxypurinol (allopurinol active metabolite), colchicine (plasma only), and uric acid. Safety was assessed by adverse events (AEs) and laboratory tests. Verinurad plasma exposure was unaffected by allopurinol. Verinurad increased the maximum observed plasma concentration (Cmax ) for allopurinol by 33%; the area under the plasma concentration-time curve (AUC) was unaffected. Oxypurinol Cmax and AUC were reduced 32% and 38%, respectively, by verinurad. Colchicine plasma exposure was unaltered by verinurad. The maximum decrease in serum urate was greater with verinurad + allopurinol (65%) than with verinurad (51%) or allopurinol (43%) alone. Compared with the baseline rate, the maximum rate of uric acid excreted in urine was +56% with verinurad, -46% with allopurinol, and unchanged with verinurad + allopurinol. No serious AEs, discontinuations due to AEs, or clinically significant laboratory abnormalities were noted. Despite decreased systemic exposure of allopurinol and oxypurinol in the presence of verinurad, the combination resulted in greater serum urate reduction compared with either drug alone and was well tolerated at the studied doses.

Investigation of the transport of xanthine dehydrogenase inhibitors by the urate transporter ABCG2.

Hyperuricemia induces gout and kidney stones and accelerates the progression of renal and cardiovascular diseases. Adenosine 5'-triphosphate-binding cassette subfamily G member 2 (ABCG2) is a urate transporter, and common dysfunctional variants of ABCG2, non-functional Q126X (rs72552713) and semi-functional Q141K (rs2231142), are risk factors for hyperuricemia and gout. A recent genome wide association study suggested that allopurinol, a serum uric acid-lowering drug that inhibits xanthine dehydrogenase, is a potent substrate of ABCG2. In this study, we aimed to examine the transport of xanthine dehydrogenase inhibitors via ABCG2. Our results show that ABCG2 transports oxypurinol, an active metabolite of allopurinol, whereas allopurinol and febuxostat, a new xanthine dehydrogenase inhibitor, are not substrates of ABCG2. The amount of oxypurinol transported by ABCG2 vesicles significantly increased in the presence of ATP, compared to that observed with mock vesicles. Since the half-life of oxypurinol is longer than that of allopurinol, the xanthine dehydrogenase-inhibiting effect of allopurinol mainly depends on its metabolite, oxypurinol. Our results indicate that the serum level of oxypurinol would increase in patients with ABCG2 dysfunction.

Why do most human liver cytosol preparations lack xanthine oxidase activity?

When investigating the potential for xanthine oxidase (XO)-mediated metabolism of a new chemical entity in vitro, selective chemical inhibition experiments are typically used. Most commonly, these inhibition experiments are performed using the inhibitor allopurinol (AP) and commercially prepared human liver cytosol (HLC) as the enzyme source. For reasons detailed herein, it is also a common practice to perfuse livers with solutions containing AP prior to liver harvest. The exposure to AP in HLC preparations could obviously pose a problem for measuring in vitro XO activity. To investigate this potential problem, an HPLC-MS/MS assay was developed to determine whether AP and its primary metabolite, oxypurinol, are retained within the cytosol for livers that were treated with AP during liver harvest. Differences in enzymatic activity for XO and aldehyde oxidase (AO) in human cytosol that can be ascribed to AP exposure were also evaluated. The results confirmed the presence of residual AP (some) and oxypurinol (all) human liver cytosol preparations that had been perfused with an AP-containing solution. In every case where oxypurinol was detected, XO activity was not observed. In contrast, the presence of AP and oxypurinol did not appear to have an impact on AO activity. Pooled HLC that was purchased from a commercial source also contained residual oxypurinol and did not show any XO activity. In the future, it is recommended that each HLC batch is screened for oxypurinol and/or XO activity prior to testing for XO-mediated metabolism of a new chemical entity.

Transport assays in filamentous fungi: kinetic characterization of the UapC purine transporter of Aspergillus nidulans.

Transport assays allow the direct kinetic analysis of a specific transporter by measuring apparent Km and Vmax values, and permit the characterization of substrate specificity profiles through competition assays. In this protocol we describe a rapid and easy method for performing uptake assays in the model filamentous ascomycete Aspergillus nidulans. Our method makes use of A. nidulans germinating conidiospores at a defined morphological stage in which most transporters show maximal expression, avoiding technical difficulties associated with the use of mycelia. In combination with the ease of construction of genetic null mutants in A. nidulans, our method allows the rigorous characterization of any transporter in genetic backgrounds that are devoid of other transporters of similar specificity. Here, we use this method to characterize the kinetic parameters and the specificity profile of UapC, a uric acid-xanthine transporter present in all ascomycetes and member of the ubiquitous Nucleobase-Ascorbate Transporter family, in specific genetic backgrounds lacking other relevant transporters.

Protection against acetaminophen-induced liver injury by allopurinol is dependent on aldehyde oxidase-mediated liver preconditioning.

Acetaminophen (APAP) overdose causes severe and occasionally fatal liver injury. Numerous drugs that attenuate APAP toxicity have been described. However these compounds frequently protect by cytochrome P450 inhibition, thereby preventing the initiating step of toxicity. We have previously shown that pretreatment with allopurinol can effectively protect against APAP toxicity, but the mechanism remains unclear. In the current study, C3HeB/FeJ mice were administered allopurinol 18h or 1h prior to an APAP overdose. Administration of allopurinol 18h prior to APAP overdose resulted in an 88% reduction in liver injury (serum ALT) 6h after APAP; however, 1h pretreatment offered no protection. APAP-cysteine adducts and glutathione depletion kinetics were similar with or without allopurinol pretreatment. The phosphorylation and mitochondrial translocation of c-jun-N-terminal-kinase (JNK) have been implicated in the progression of APAP toxicity. In our study we showed equivalent early JNK activation (2h) however late JNK activation (6h) was attenuated in allopurinol treated mice, which suggests that later JNK activation is more critical for the toxicity. Additional mice were administered oxypurinol (primary metabolite of allopurinol) 18h or 1h pre-APAP, but neither treatment protected. This finding implicated an aldehyde oxidase (AO)-mediated metabolism of allopurinol, so mice were treated with hydralazine to inhibit AO prior to allopurinol/APAP administration, which eliminated the protective effects of allopurinol. We evaluated potential targets of AO-mediated preconditioning and found increased hepatic metallothionein 18h post-allopurinol. These data show metabolism of allopurinol occurring independent of P450 isoenzymes preconditions the liver and renders the animal less susceptible to an APAP overdose.

Modelling the reduced xanthine oxidase in active sulfo and inactive desulfo forms.

Synthesis of two complexes, [NBu(n)(4)][Mo(IV)O(mnt)(S-Tol)(N-N)] (N-N = 2,2'-bipyridine (1a) or 1,10-phenanthroline (1b); mnt = maleonitriledithiolate; S-Tol = toluenethiol) are reported. These on treatment with H(2)S generate the corresponding [NBu(n)(4)][Mo(IV)O(mnt)(SH)(N-N)] (2a and 2b) complexes bearing the susceptible hydrosulfide coordination. 2a (and 2b) upon chemical oxidation show EPR spectra with the appearance of a Mo(V) signal at = 1.976 (for 2a and 2b). Such EPR signal changed to another slow Mo(V) signal at = 1.949 at the expense of the initial signal. This conversion is accelerated in the presence of trace amount of moisture in the solvent. These data are similar to the Moco isolated from the xanthine oxidase (XO) as reported by Bray. 2a (and 2b) responds to one electron electrochemical oxidation and the generated pentavalent species responds to proton coupled electron transfer reaction. A predominantly metal centered HOMO is observed in 2a (and 2b) from DFT calculations. In the inhibited Moco of XO bearing a -SH moiety, the HOMO shows considerably less electron density residing on the Mo d(xy) orbital and maximum electron density is distributed to the phospho-ester group rendering the Mo(IV) center incapable of participating in the electron transfer process manifesting inhibition.

Relationship between serum urate and plasma oxypurinol in the management of gout: determination of minimum plasma oxypurinol concentration to achieve a target serum urate level.

The treatment of gout requires a lowering of serum urate (SU) levels, and allopurinol is the drug that is most commonly used for this purpose. The objectives of this study were to define the relationships between allopurinol dose on the one hand and plasma oxypurinol, renal function, and SU levels on the other and to determine the minimum plasma oxypurinol concentration that would result in a target level of <6 mg/dl (0.36 mmol/l) of SU. For this purpose, 82 patients who had been receiving allopurinol for at least 1 month were recruited. Patients with SU <6 mg/dl were followed up quarterly for 12 months. In patients with SU ≥6 mg/dl, the dose of allopurinol was increased to bring the level of SU to <6 mg/dl. These patients were followed up once a month until the SU level remained at <6 mg/dl for 3 consecutive months; thereafter they were seen quarterly. SU, creatinine, and plasma oxypurinol were measured 6-9 hours after administration of the allopurinol dose. There were significant inverse correlations between creatinine clearance (CrCl) and plasma oxypurinol (P = 0.002), between allopurinol dose and SU (P < 0.0001) and between plasma oxypurinol and SU (P < 0.0001). Using receiver operating characteristic analysis, the target SU of <6 mg/dl was achieved in 75% of serum samples with plasma oxypurinol levels of >100 µmol/l (15.2 mg/l). Increasing the allopurinol dose resulted in increased plasma oxypurinol and reduced SU concentrations. Plasma oxypurinol concentrations >100 µmol/l were required to achieve SU <6 mg/dl.

Mechanism of inhibition of xanthine oxidoreductase by allopurinol: crystal structure of reduced bovine milk xanthine oxidoreductase bound with oxipurinol.

Inhibitors of xanthine oxidoreductase block conversion of xanthine to uric acid and are therefore potentially useful for treatment of hyperuricemia or gout. We determined the crystal structure of reduced bovine milk xanthine oxidoreductase complexed with oxipurinol at 2.0 A resolution. Clear electron density was observed between the N2 nitrogen of oxipurinol and the molybdenum atom of the molybdopterin cofactor, indicating that oxipurinol coordinated directly to molybdenum. Oxipurinol forms hydrogen bonds with glutamate 802, arginine 880, and glutamate 1261, which have previously been shown to be essential for the enzyme reaction. We discuss possible differences in the hypouricemic effect of inhibitors, including allopurinol and newly developed inhibitors, based on their mode of binding in the crystal structures.

Pharmacokinetic and pharmacodynamic interaction between allopurinol and probenecid in healthy subjects.

BACKGROUND AND OBJECTIVE: Combination therapy with allopurinol and probenecid is used to treat tophaceous gout in patients who do not respond sufficiently to allopurinol alone. However, the potential interaction between these drugs has not been systematically investigated. The objective of this study was to investigate the pharmacokinetics and hypouricaemic effect of oxypurinol (the active metabolite of allopurinol) and probenecid when administered alone and in combination in healthy subjects. METHODS: An open-label, randomized, three-way crossover clinical trial was conducted in 12 healthy adults. Subjects were randomized to receive treatment for 7 days with allopurinol (150 mg twice daily), probenecid (500 mg twice daily) or combination therapy with both drugs, with a 7-day washout period between treatments. Venous blood samples were collected predose (at 0 hours) and 1, 2, 3, 4, 6, 8, 10 and 12 hours after dosage for determination of oxypurinol and/or probenecid concentrations. Plasma and urinary urate concentrations were determined on each study day and at the end of each washout period. Pharmacokinetic and pharmacodynamic parameters were analysed using two-way ANOVA. RESULTS: Coadministration of allopurinol and probenecid significantly reduced average steady-state plasma oxypurinol concentrations (mean+/-SD: allopurinol alone 9.7+/-2.1 mg/L vs combination 5.1+/-1.0 mg/L, p<0.001). Probenecid concentrations were unaffected. Plasma urate concentrations decreased (p<0.01) during allopurinol therapy (0.16+/-0.05 mmol/L), probenecid therapy (0.13+/-0.02 mmol/L) and combination therapy (0.09+/-0.02 mmol/L) compared with baseline (0.30+/-0.05 mmol/L). CONCLUSION: Coadministration of allopurinol and probenecid to healthy subjects had a greater hypouricaemic effect than either allopurinol or probenecid alone, despite a reduction in plasma oxypurinol concentrations when the drugs were taken concomitantly.

Clinical pharmacokinetics and pharmacodynamics of allopurinol and oxypurinol.

Allopurinol is the drug most widely used to lower the blood concentrations of urate and, therefore, to decrease the number of repeated attacks of gout. Allopurinol is rapidly and extensively metabolised to oxypurinol (oxipurinol), and the hypouricaemic efficacy of allopurinol is due very largely to this metabolite. The pharmacokinetic parameters of allopurinol after oral dosage include oral bioavailability of 79 +/- 20% (mean +/- SD), an elimination half-life (t((1/2))) of 1.2 +/- 0.3 hours, apparent oral clearance (CL/F) of 15.8 +/- 5.2 mL/min/kg and an apparent volume of distribution after oral administration (V(d)/F) of 1.31 +/- 0.41 L/kg. Assuming that 90 mg of oxypurinol is formed from every 100mg of allopurinol, the pharmacokinetic parameters of oxypurinol in subjects with normal renal function are a t((1/2)) of 23.3 +/- 6.0 hours, CL/F of 0.31 +/- 0.07 mL/min/kg, V(d)/F of 0.59 +/- 0.16 L/kg, and renal clearance (CL(R)) relative to creatinine clearance of 0.19 +/- 0.06. Oxypurinol is cleared almost entirely by urinary excretion and, for many years, it has been recommended that the dosage of allopurinol should be reduced in renal impairment. A reduced initial target dosage in renal impairment is still reasonable, but recent data on the toxicity of allopurinol indicate that the dosage may be increased above the present guidelines if the reduction in plasma urate concentrations is inadequate. Measurement of plasma concentrations of oxypurinol in selected patients, particularly those with renal impairment, may help to decrease the risk of toxicity and improve the hypouricaemic response. Monitoring of plasma concentrations of oxypurinol should also help to identify patients with poor adherence. Uricosuric drugs, such as probenecid, have potentially opposing effects on the hypouricaemic efficacy of allopurinol. Their uricosuric effect lowers the plasma concentrations of urate; however, they increase the CL(R) of oxypurinol, thus potentially decreasing the influence of allopurinol. The net effect is an increased degree of hypouricaemia, but the interaction is probably limited to patients with normal renal function or only moderate impairment.

[Genetically determined gout: characteristics of the course].

Analysis of clinical-roentgen-laboratory features of the course of hereditarily determined gout in 74 patients is represented. It is exhibited that hereditarily induced gout begins at the young age and is accompanied by the acute disturbance of purine exchange resulting in serious relapsing course of the articular (with availability of radiological attributes of osteal destruction) and the renal syndromes (urate nephrolithiasis, immune complex glomerulonephritis, tubulointerstitional nephritis) as well as in the early occurrence and rapidly progressing chronic renal insufficiency. The disease is accompanied by high frequency of the cardiovascular pathologies negatively influencing the mean lifetime of patients.

Are allopurinol and metabolites found in HPRT deficient erythrocytes responsible for increased NAD synthesis?

Aim of this study was to ascertain whether allopurinol, usually administered to hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficient patients, or metabolites abnormally increased in HPRT deficient erythrocytes (NAD, PPribP) could be directly responsible for the reported increased activities of nicotinic acid phosphoribosyltransferase (NAPRT) and NADsynthetase (NADs) in these patients. No direct effect of the mentioned metabolites was demonstrated.

Crystal structures of the active and alloxanthine-inhibited forms of xanthine dehydrogenase from Rhodobacter capsulatus.

Xanthine dehydrogenase (XDH), a complex molybdo/iron-sulfur/flavoprotein, catalyzes the oxidation of hypoxanthine to xanthine followed by oxidation of xanthine to uric acid with concomitant reduction of NAD+. The 2.7 A resolution structure of Rhodobacter capsulatus XDH reveals that the bacterial and bovine XDH have highly similar folds despite differences in subunit composition. The NAD+ binding pocket of the bacterial XDH resembles that of the dehydrogenase form of the bovine enzyme rather than that of the oxidase form, which reduces O(2) instead of NAD+. The drug allopurinol is used to treat XDH-catalyzed uric acid build-up occurring in gout or during cancer chemotherapy. As a hypoxanthine analog, it is oxidized to alloxanthine, which cannot be further oxidized but acts as a tight binding inhibitor of XDH. The 3.0 A resolution structure of the XDH-alloxanthine complex shows direct coordination of alloxanthine to the molybdenum via a nitrogen atom. These results provide a starting point for the rational design of new XDH inhibitors.

Photoreactivation of alloxanthine-inhibited xanthine oxidase.

Alloxanthine-inhibited xanthine oxidase (XOD) was found to be photoreactivated by irradiation of light of wavelengths in the range of 340-430 nm. The enzyme activity can be fully controlled to be on or off by many dark-light cycles. Electron spin resonance measurement shows the appearance of the molybdenum (V) ion and the reduced form of flavin adenine dinucleotide (FADH.) radical signals after irradiation of the alloxanthine-XOD complex. Electronic-absorption spectrum also shows the bleaching of Fe/S and flavin adenine dinucleotide chromophores at 375 and 450 nm as well as broad-band absorption of FADH. in the range of 500-700 nm. The quantum yield of photoreactivation of the enzyme activity is approximately 0.06. A photoinduced intraenzyme electron-transfer model is proposed to rationalize the photoreactivation process.

Effect of glucose infusion on the renal transport of purine bases and oxypurinol.

The effect of glucose infusion on renal handling of purine bases and oxypurinol was examined in 6 normal subjects. Five hundred milliliters of 1.1 M glucose solution were administered intravenously in 1 h. Fractional clearances of uric acid, xanthine and oxypurinol were significantly increased during glucose infusion, but that of hypoxanthine was not changed, while a 1-hour infusion of 500 ml of 1.1 M mannitol had no effect on the fractional clearances of purine bases and oxypurinol. These data indicate that the effect of glucose infusion on the renal clearances of uric acid, xanthine and oxypurinol was not related to osmotic diuresis but induced by glycosuria and/or hyperglycemia. Accordingly, the glycosuria- and/or hyperglycemia-induced decrease in the biological half-life of oxypurinol must be considered in the administration of allopurinol to gouty patients with uncontrolled diabetes mellitus.