Screening method for inherited disorders of purine and pyrimidine metabolism by capillary electrophoresis with reversed electroosmotic flow

Capillary electrophoresis with electroosmotic flow reversed by cationic surfactant for diagnosis of purine and pyrimidine inherited enzyme deficiencies is reported. Final separation conditions consist of 45 mM borate, 55 mM N-tris[hydroxymethyl]methylglycine, 10 mM tartrate, 1 mM cetyltrimethylammonium bromide and 0.44% tetrabutylammonium hydroxide-2-amino-2-methyl-1,3-propanediol (pH 8.6). Average sensitivity (2.51 microM), reproducibility of migration times (run-to-run C.V. < or = 0.6%, day-to-day C.V. < or = 2.5%), linearity (R2>0.994) and imprecision (mean intra-assay RSD 4.7% and inter-assay RSD 6.6%) of the method are acceptable for diagnostic purposes. Applicability of the method is demonstrated on urine samples from patients with enzymatically proven enzyme deficiencies.

Capillary electrophoresis for detection of inherited disorders of purine and pyrimidine metabolism: a selective approach

We developed a capillary electrophoresis method as a diagnostic tool for purine and pyrimidine metabolic disorders. Optimal conditions allowed the separation of the major diagnostic metabolites in urine samples within an analysis time of 10 min and with a separation efficiency of about 350,000 theoretical plates/m. The diagnostically important metabolites (adenine, adenosine, 2-deoxyadenosine, 2-deoxyguanosine, 2,8-dihydroxyadenine, guanosine, hypoxanthine, orotidine, orotic acid, and creatinine) were detectable at concentrations of 1.0-5.7 micromol/L. The method gives a linear calibration curve for tested purine and pyrimidine derivatives within the range of 5-500 micromol/L (r > 0.996) The coefficients of variation for the within- and between-day imprecisions were less than 3.2 and 5.8%, respectively. Characteristic abnormalities were detected in the electropherograms of urine samples from patients with purine and pyrimidine enzyme deficiencies. We provide electrophoretic and spectral characteristics of intermediates in purine and pyrimidine metabolism and possible artifacts from medication and their UV-absorbing compounds. Our method allows the detection of the majority of inborn errors of purine and pyrimidine metabolism.

Using artificial neural networks to model the urinary excretion of total and purine derivative nitrogen fractions in cows

A dataset of 177 individual nitrogen balances from dry and lactating cows was split in two independent groups: training dataset (n = 130) and challenge dataset (n = 47). The training dataset was used to develop multiple linear regressions (MLR) and artificial neural networks (ANN) aimed at predicting the urinary excretion of total (NURI) and that of purine derivative nitrogen (PDN). Input variables for the prediction of NURI were crude protein (CP) intake, effective degradability of non-protein dry matter (DM), neutral detergent fiber (NDF) content of the diet, live weight and milk yield. Live weight, total carbohydrate intake, the ratio of non-protein DM degraded to CP degraded and milk yield corrected for DM intake were entered to predict PDN. The regression between predicted and observed values for the training dataset showed a better statistical accuracy of ANN than did MLR models, especially for PDN. The evaluation of the two models on the challenge dataset showed similar determination coefficients, either when predicting total nitrogen excretion (0.623 and 0.614 for ANN and MLR, respectively) or PDN (0.688 and 0.666, for ANN and MLR, respectively). Moreover, both approaches were affected by a tendency to under-predict both targets at high levels of NURI and PDN. However, with the ANN approach, it is possible to study the response of the model to modifications of individual inputs by the so-called response analysis. This unique feature could be used to study the effect of different physiological situations as well as providing hypotheses for additional research.

Effect of norepinephrine on the urinary excretion of purine bases and oxypurinol

To examine whether norepinephrine affects the plasma concentrations and urinary excretion of purine bases and oxypurinol, we orally administered allopurinol (300 mg) to 5 healthy subjects and 9 hours later intravenously administered norepinephrine (12 to 20 microg/kg body weight), which causes a more than 10 mm Hg increase in diastolic pressure for 2 hours. Norepinephrine decreased the urinary excretion of uric acid by 33% (P <.01), oxypurinol by 32% (P <.01), and xanthine by 51% (P <.01), as well as the fractional clearance of uric acid by 32% (P <.01), oxypurinol by 24% (P <.05), and xanthine by 21% (P <.05) when measured 1 to 2 hours after administration. These results indicate that norepinephrine decreases the urinary excretion of uric acid, oxypurinol, and xanthine, probably via hemodynamic change. It is also suggested that the hypouricemic effect of allopurinol may be more potent than that expected in gout patients with enhanced sympathetic tone, such as in salt-sensitive hypertension.

Effect of fenofibrate on plasma concentration and urinary excretion of purine bases and oxypurinol

OBJECTIVE

To investigate whether fenofibrate increases the clearance of purine bases (hypoxanthine, xanthine, uric acid) and oxypurinol.

METHODS

We administered fenofibrate (150 mg) 3 times a day for 3 days, and then allopurinol (300 mg) 4 h after the last administration of fenofibrate, to 5 healthy subjects. Ten hours later, a clearance study was done.

RESULTS

Following 3 day administration of fenofibrate, fractional clearance of xanthine, uric acid, and oxypurinol increased by 41% (p < 0.05), 101% (p < 0.01), and 51% (p < 0.01), respectively, compared to baseline values, while the respective plasma concentrations decreased by 46% (p < 0.05), 46% (p < 0.05), and 19% (p < 0.05).

CONCLUSION

Our results suggest that fenofibrate, fenofibric acid, or fenofibrate derivatives can increase fractional clearance of xanthine, uric acid, and oxypurinol by acting on their common renal pathways. It is suggested that the hypouricemic effect of combination therapy using allopurinol and fenofibrate may be less than additive.

Determination of urinary methylated purine pattern by high-performance liquid chromatography

We describe the group selective separation and quantification of unmodified and modified purines in human urine by high-performance reverse phase liquid chromatography. The pattern of oxypurines and methylated purines: hypoxanthine (Hx), xanthine (X), 1-methyl hypoxanthine (1-MHx), 1-methyl guanine (1-MG), 3-methyl guanine (3-MG), 7-methyl guanine (7-MG), 1-methyl xanthine (1-MX), 3-methyl xanthine (3-MX), 7-methyl xanthine (7-MX), 1,7-dimethyl guanine (1,7-dMG), 1,3-dimethyl xanthine (1,3-dMX), 1,7-dimethyl xanthine (3,7-dMX) and 1,3,7-trimethyl xanthine (1,3,7-tMX) were determined in a single run in urine of a healthy subject and a gout patient before and after treatment with allopurinol. This method may be useful to investigate the urinary pattern of methylated bases in diseases involving purine metabolism.

Effect of furosemide on renal excretion of oxypurinol and purine bases

To examine whether furosemide affects the plasma concentration and urinary excretion of purine bases and oxypurinol, we administered allopurinol (300 mg) orally to 6 healthy subjects and then administered furosemide (20 mg) intravenously 10 hours later. Furosemide (20 mg) decreased the urinary excretion of uric acid by 40% (P < .01), oxypurinol by 39% (P < .05), and xanthine by 43% (P < .05) and the fractional clearance of uric acid by 45% (P < .01) and oxypurinol by 34% (P < .05) when measured 1 to 2 hours after administration. Moreover, furosemide increased the plasma concentration of uric acid by 6% at 1.5 hours after administration. These results indicate that furosemide may decrease the urinary excretion of uric acid and oxypurinol by acting on their common renal transport pathway(s). In addition, it is suggested that the effect of furosemide on oxypurinol is clinically important, since the hypouricemic effect of allopurinol may become more potent as a result.

Effect of the tropical forage calliandra on microbial protein synthesis and ecology in the rumen

AIMS

To determine the effect of condensed tannins in Calliandra calothyrsus (calliandra) on rumen microbial function.

METHODS AND RESULTS

Microbial populations, ruminal protein synthesis and fermentation end-products were measured in sheep fed roughage hay supplemented with calliandra (30%), with and without inclusions of polyethylene glycol (PEG) to counteract the effect of tannin. Molecular and conventional enumeration techniques were used to quantify rumen bacteria, fungi and protozoa, and protein synthesis was predicted from estimates of urinary purine excretion. The total number of cellulolytic bacteria, including populations of Fibrobacter succinogenes and Ruminococcus spp., was significantly lower in sheep supplemented with calliandra and these populations increased when animals were treated with PEG. By contrast, protozoa and fungi and the microbial group containing Bacteroides-Porphyromonas-Prevotella bacteria appeared to be less affected. The efficiency of microbial protein synthesis in the rumen was not altered significantly.

CONCLUSION

Calliandra caused significant shifts in rumen microbial populations without changing the efficiency of protein synthesis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The effect of calliandra tannins on rumen digestion may result more from complexing with nutrients than direct inhibition of micro-organisms.

Analysis of purines in urinary calculi by high-performance liquid chromatography

A high-pressure liquid chromatography method has been developed for the analysis in urinary calculi of six purines: uric acid, 2, 8-dihydroxyadenine, xanthine, hypoxanthine, allopurinol, and oxypurinol. Separation was conducted isocratically on a reversed-phase column, using 50 mM phosphate buffer (pH 5.5) / methanol (97/3, v/v) as mobile phase. Limits of detection, depending on compound, ranged from 7 to 28 microg/g stone weight. Hitherto, no reports have appeared on other purines present with uric acid in stones, due to lack of a sensitive and specific analytical method. We have now found that all calculi with more than 4% uric acid also contained 1-methyluric and 7-methyluric acids and trace amounts of hypoxanthine, xanthine, and 2,8-dihydroxyadenine. Accurate identification and quantitation of purines in urinary calculi are important for the diagnosis of rare metabolic diseases leading to urolithiasis (xanthinuria, dihydroxyadeninuria), as well as for prevention of iatrogenic complications during treatment with allopurinol of uric acid urolithiasis. The method may be used for reference purposes in clinical laboratories and for research on the pathogenesis of urolithiasis in disorders of purine metabolism.

Effect of losartan potassium, an angiotensin II receptor antagonist, on renal excretion of oxypurinol and purine bases

OBJECTIVE

To examine whether losartan affects the plasma concentrations and urinary excretion of purine bases and oxypurinol.

METHODS

We administered allopurinol (300 mg) and then 9 h later losartan potassium (100 mg) to 5 healthy subjects.

RESULTS

The urinary excretion of uric acid increased by 3.9- and 2.6-fold, and that of oxypurinol by 2- and 1.8-fold, at 1 to 2 h and at 2 to 3 h, respectively, after administration of losartan potassium. The fractional clearance of uric acid was increased by 4.3- and 3.2-fold, oxypurinol by 2.3- and 2.1-fold, and xanthine by 1.32- and 1.26-fold, at 1 to 2 h and at 2 to 3 h, respectively, after administration of losartan potassium. The plasma concentrations of uric acid decreased by 8% and 16%, oxypurinol by 7% and 11%, and xanthine by 42% and 45%, at 1.5 and 2.5 h, respectively, after oral administration.

CONCLUSION

These results suggest that losartan potassium could increase urinary excretion of uric acid, xanthine, and oxypurinol by acting on their common renal transport pathways, since it was found that uric acid may share a renal transport pathway with oxypurinol and xanthine. It is also suggested that the effect of losartan potassium on oxypurinol and uric acid is clinically important, since the hypouricemic effect of a combination therapy using allopurinol and losartan potassium may be less than additive, while the uricosuric effect of losartan potassium may increase the frequency of calculi in the urinary tract.

Effect of branched-chain amino acids on the plasma concentration of uridine does not occur via the action of glucagon or insulin

To examine whether branched-chain amino acids affect the plasma concentration of uridine, we administered branched-chain amino acids (L-isoleucine, 2.85 g, L-leucine 5.71 g, and L-valine, 3.43 g) orally to 6 healthy subjects. Plasma uridine and glucose decreased by 44% and 12%, respectively, together with an increase in plasma isoleucine, leucine, and valine 90 minutes after administration. However, branched-chain amino acids did not affect the plasma concentration and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid) and uridine or the plasma concentration of insulin, glucagon, and cyclic adenosine monophosphate (cAMP). Since small amounts of regular insulin, which were found to decrease plasma glucose more than the amino acids, did not decrease the plasma concentration of uridine, these results suggest that plasma uridine was decreased by a direct effect of the branched-chain amino acids on the cellular uptake and/or release of uridine.

Purine loss after repeated sprint bouts in humans

The influence of the number of sprint bouts on purine loss was examined in nine men (age 24.8 +/- 1.6 yr, weight 76 +/- 3.9 kg, peak O(2) consumption 3.87 +/- 0.16 l/min) who performed either one (B1), four (B4), or eight (B8) 10-s sprints on a cycle ergometer, 1 wk apart, in a randomized order. Forearm venous plasma inosine, hypoxanthine (Hx), and uric acid concentrations were measured at rest and during 120 min of recovery. Urinary inosine, Hx, and uric acid excretion were also measured before and 24 h after exercise. During the first 120 min of recovery, plasma inosine and Hx concentrations, and urinary Hx excretion rate, were progressively higher (P < 0.05) with an increasing number of sprint bouts. Plasma uric acid concentration was higher (P < 0.05) in B8 compared with B1 and B4 after 45, 60, and 120 min of recovery. Total urinary excretion of purines (inosine + Hx + uric acid) was higher (P < 0. 05) at 2 h of recovery after B8 (537 +/- 59 micromol) compared with the other trials (B1: 270 +/- 76; B4: 327 +/- 59 micromol). These results indicate that the loss of purine from the body was enhanced by increasing the number of intermittent 10-s sprint bouts.

Effect of replacing alfalfa silage with high moisture corn on ruminal protein synthesis estimated from excretion of total purine derivatives

Twenty-four multiparous dairy cows (eight with ruminal cannulae) were blocked by days in milk and assigned to six balanced 4 x 4 Latin squares with 21-d periods. The four diets, formulated from alfalfa silage plus a concentrate mix based on ground high moisture ear corn, contained (dry matter basis): 1) 20% concentrate, 80% alfalfa silage (24% nonfiber carbohydrate; NFC), 2) 35% concentrate, 65% alfalfa silage (30% NFC), 3) 50% concentrate, 50% alfalfa silage (37% NFC), or 4) 65% concentrate, 35% alfalfa silage (43% NFC). Soybean meal and urea were added to make diets isonitrogenous with equal nonprotein nitrogen (NPN) (43% of total N). Total urine was collected with indwelling Folley catheters for 24 h during each period. There was no effect of diet on urinary creatinine excretion (average 29 mg/kg of BW/d). There were quadratic effects of diet on total urinary ecretion of allantoin, uric acid, and purine derivatives (allantoin plus uric acid), and on ruminal synthesis of microbial N estimated from purine derivatives; maxima occurred at about 35% dietary NFC. Urinary excretion also was estimated with spot urine samples from creatinine concentration and the mean daily creatinine excretion. Daily excretion of allantoin, uric acid, and purine derivatives estimated from spot urine sampling followed the same pattern as that observed with total collection; differences between measured and estimated urine volume were significant only for 35% dietary concentrate. Spot urine sampling appeared to yield satisfactory estimates of purine derivative excretion. Maximal urea N excretion was estimated to occur at about 31% dietary NFC. Milk allantoin secretion increased linearly with concentrate and accounted for 4 to 6% of the total purine derivative excretion. Microbial yield was maximal at 35% dietary NFC, suggesting that this was the optimal level for utilization of dietary NPN from alfalfa silage and other sources.

Effects of fructose and xylitol on the urinary excretion of adenosine, uridine, and purine bases

To examine whether fructose and xylitol increase the plasma concentration and urinary excretion of adenosine, as well as uridine and purine bases (hypoxanthine, xanthine, and uric acid), we intravenously administered xylitol and, 2 weeks later, fructose, to five healthy subjects. Analyses of blood and urine samples obtained during these infusion studies demonstrated that fructose increased the urinary excretion of adenosine and uridine 11.9- and 105.5-fold, respectively, and caused only a small increase in the plasma concentrations of uridine and purine bases. It was further demonstrated that xylitol increased the urinary excretion of uridine 58.4-fold, with a marked increase in the plasma concentrations of purine bases and uridine but without an increase in the urinary excretion of adenosine. However, neither infusion increased the plasma concentration of adenosine. These results suggest that in addition to many organs, including the liver, fructose is significantly metabolized by an abrupt adenosine triphosphate (ATP) consumption in the kidney, leading to an increase in the urinary excretion of adenosine and uridine. They also suggest that xylitol is not significantly metabolized in the kidney.

Effect of glucose on the plasma concentration and urinary excretion of uridine and purine bases

To examine whether glucose increases the plasma concentration of purine bases and uridine, 75 g glucose was administered orally to eight healthy subjects and two patients with hyperuricemia. The plasma concentration of uridine increased by 21%, 25%, and 20% 30, 60, and 90 minutes after administration of glucose, respectively. However, urinary excretion of uridine was not affected, nor were the plasma concentrations and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid). These results suggest that the glucose-induced increase in plasma uridine was not concomitant with adenosine triphosphate (ATP) consumption-induced purine degradation, but instead was ascribable to a uridine diphosphate (UDP)-glucose consumption-induced pyrimidine degradation (UDP-glucose-->UDP-->uridine monophosphate [UMP]-->uridine).

Simultaneous determination of purine metabolites, creatinine and pseudouridine in ruminant urine by reversed-phase high-performance liquid chromatography

Determination of purine metabolites, pseudouridine and creatinine in both bovine and ovine urine using high-performance liquid chromatography (HPLC) is described. Following dilution and filtration, urine samples were analysed directly. Separation and quantification was achieved using a Spherisorb ODS II C18 column (250x4.6 mm I.D.) under isocratic conditions. The mobile phase contained 7.5 mM ammonium dihydrogen phosphate, 10 mM sodium 1-heptane sulphonic acid and 1.0 mM triethylamine at pH 3.0. Chromatography was achieved at a flow-rate of 1.0 ml/min and monitoring column effluent at 218 nm. Total analysis time was 60 min. Recovery of all compound standards added to urine was above 96%. In all cases, close spectral matches of compound standards and corresponding identified peaks in ovine and bovine urine were obtained. Lowest detectable concentrations of allantoin, uric acid, xanthine, hypoxanthine, creatinine and pseudouridine were 1.1, 1.0, 1.0, 3.0 and 0.4 micromol/l, respectively. Advantages of simultaneous determination of purine metabolites, creatinine and pseudouridine in ruminant urine collected from both sheep and cattle exist over current methods.

Effects of rumen-undegradable protein and feed intake on purine derivative and urea nitrogen: comparison with predictions from the Cornell Net Carbohydrate and Protein System

Six multiparous Holstein cows were used in a 6 x 6 Latin square to investigate the ability of the Cornell Net Carbohydrate and Protein System to predict accurately rumen microbial yield, plasma urea N, and milk urea N. Estimations for microbial protein yield were compared with the measured excretion of purine derivative N in urine. A 3 x 2 factorial arrangement of treatments was adopted. Three concentrations of a rumen-undegradable protein (RUP) supplement (4.5, 14.9, and 29.1% of dry matter intake) and two levels of feed restriction (90 and 80% of ad libitum intake) were the corresponding factors. No effect of concentration of RUP supplement or feed restriction was detected on the excretion of purine derivative N in urine (mean, 18.5 g/d). Conversely, the Cornell system predicted a linear decrease in metabolizable protein from bacteria as the concentration of the RUP supplement increased. The Cornell system also predicted a significant reduction in metabolizable protein of microbial origin as feed restriction was increased. Measured values and values derived from the Cornell system for plasma and milk urea N increased linearly as the concentration of the RUP supplement increased. The Cornell system overpredicted milk urea N for cows consuming the highest RUP concentration. Predictions by the Cornell Net Carbohydrate and Protein System were of limited value because the empirical nature of the model is insufficiently rigorous to yield accurate predictions under the conditions described herein.

Effect of glucagon on the plasma concentration of uridine

To determine whether glucagon affects the plasma concentration of uridine, we administered 100 mL physiological saline containing 1 mg glucagon or 100 mL physiological saline alone intravenously over 1 hour to healthy subjects. Glucagon decreased the plasma concentration of uridine from 5.72 +/- 1.05 to 4.80 +/- 0.60 micromol/L but increased the concentrations of cyclic adenosine monophosphate (cAMP) in plasma and pyruvic acid and lactic acid in blood 59-, 1.4-, and 1.3-fold, respectively. Although glucagon increased urinary excretion of uric acid, it did not affect the plasma concentration of purine bases (hypoxanthine, xanthine, and uric acid) or urinary excretion of oxypurines and uridine, indicating that glucagon does not affect purine degradation and suggesting that glucagon does not affect adenosine triphosphate (ATP) consumption-induced pyrimidine degradation. In contrast, physiological saline did not affect any of the measured variables. These results suggest that glucagon enhanced Na+-dependent uridine uptake from the blood into the cells, since glucagon stimulates Na+-dependent uridine uptake into cells in vitro.

Xylitol-induced increase in the plasma concentration and urinary excretion of uridine and purine bases

To determine whether xylitol increases the plasma concentration and urinary excretion of uridine together with purine bases, we administered xylitol (0.6 g/kg weight) intravenously to six normal subjects using a 10% xylitol solution. Xylitol infusion increased the plasma concentration and urinary excretion of uridine, as well as purine bases, while it decreased both the concentrations of inorganic phosphate in plasma and pyruvic acid in blood and increased the blood concentration of lactic acid. These results suggest that an increase in the plasma concentration and urinary excretion of uridine is ascribable to increased pyrimidine degradation following purine degradation induced by xylitol.

Purines and pyrimidines determination in urine using high-performance liquid chromatography

Single purine and pyrimidine bases are involved in two fundamental metabolic pathways that lead to formation of the building stones of DNA and RNA. Purine and pyrimidine nucleotides are also critically important metabolites in many cellular functions. The main breakdown of purines and pyrimidines produces uric acid and B-minoacids, respectively. Therefore, the study of purine and pyrimidine compounds in body fluid has high clinical relevance. We report, in this work, our experience in purines and pyrimidines determination in urine from children presenting with a clinical picture suggesting an inborn these pathways.

Mixed effects of 2,6-dithiopurine against cyclophosphamide mediated bladder and lung toxicity in mice

2,6-Dithiopurine (DTP) has been proposed as a possible chemopreventive agent because of its ability to react with electrophiles. Acrolein, an electrophilic metabolite of cyclophosphamide (CP) involved in the toxicities of this anticancer drug, can be scavenged by DTP. The present study examined the effect of DTP treatment on CP-mediated bladder and lung toxicity in male ICR mice. Mice fed a diet containing 4% DTP that were treated intraperitoneally (i.p.) with 350 mg/kg CP showed no significant bladder damage (measured as bladder blood content at 48 h) with respect to the group fed a control diet. DTP (50 and 100 mg/kg), given i.p. 0.5 and 7 h after the initial injection of CP, also prevented the bladder damage when compared with the group receiving CP alone. Surprisingly, although neither parenteral CP nor DTP alone caused any mortality at these doses, the combined treatment resulted in 67% mortality within 3 days. At 24 h after CP + DTP, blood urea nitrogen was elevated 6-fold and urine volumes decreased by 70%. Histopathological analyses revealed a diffuse myocardial degeneration and necrosis, severe granular degeneration in the liver, abundant cellularity and infiltrates in interalveolar spaces in the lung and swollen nephron epithelial cells with some necrosis. All mice survived treatment when the dose of CP was lowered to 250 and 25-75 mg/kg DTP was given i.p. 0.5 and 7 h after CP. These DTP regimens reduced the degree of CP-induced lung toxicity, measured by [3H]thymidine incorporation into lung DNA 7 days after CP, in a dose-dependent manner. DTP (75 mg/kg) also reduced CP-induced lung fibrosis estimated by lung hydroxyproline content 28 days after CP. Analyses of urine from mice given CP + DTP revealed large amounts of the metabolic product dithiouric acid, smaller amounts of the parent DTP and several smaller peaks. The major unique metabolite peak was collected and analyzed by mass spectrometry, but did not correspond to either acrolein-DTP or acrolein-dithiouric acid. Thus, either very small amounts of an acrolein adduct are generated, the adduct is broken down to an unidentified product, or the ability of DTP to prevent CP-induced lung and bladder damage is related to some other mechanism. The possibility that mercapturic acid metabolites of acrolein released the parent electrophile in the urine was not supported by the finding that probenecid did not prevent CP-induced bladder toxicity.

Effect of allopurinol and benzbromarone on the concentration of uridine in plasma

To investigate whether allopurinol and benzbromarone affect the concentration of uridine in plasma, allopurinol or benzbromarone were administered to patients with gout for 3 to 6 months. Allopurinol decreased the concentrations of uridine and uric acid in plasma and the urinary excretion of uric acid, but increased the plasma concentration and urinary excretion of oxypurines and orotidine. Benzbromarone decreased the concentration of uric acid in plasma and increased the excretion of uric acid in urine. However, it did not affect the plasma concentration of uridine or oxypurines or the urinary excretion of oxypurines or orotidine. These results suggest that orotidilytic decarboxylase was inhibited by allopurinol and oxypurinol ribonucleotides and/or that phosphoribosyl pyrophosphate (PRPP) was consumed by conversion from hypoxanthine, allopurinol, and oxypurinol to the respective ribonucleotides, resulting in a decrease in the de novo synthesis of pyrimidine leading to the decreased concentration of uridine in plasma. Furthermore, it was suggested that benzbromarone did not affect the de novo synthesis of pyrimidine or purine.

Excretion of purine derivatives by Holstein cows abomasally infused with incremental amounts of purines

Five multiparous, ruminally cannulated Holstein cows (two lactating and three dry) weighing (X +/- SD) 667 +/- 35 kg were used to study the effect of abomasal purine infusion on the excretion of purine derivatives. Cows were fed corn silage four times daily at 90% of ad libitum intake (X = 9.16 kg of dry matter/d). Purines were infused into the abomasum as brewer's yeast suspensions in five incremental amounts (0 to 380 mmol/d) during five experimental periods according to a 5 x 5 Latin square design. Periods were 7 d; purine infusions were conducted during the last 4 d, and urine was collected during the last 3 d of each period. Ruminal purine outflow in all cows was measured during an experimental period immediately preceding and immediately following the five infusion periods and in each cow during the 0-mmol/d infusion period of the experiment. The relationship between total (milk plus urine) daily excretion of purine derivatives (allantoin plus uric acid) and total (abomasal infusion plus ruminal outflow) daily purine flow was quantified by linear regression analysis and was described by the relationship: Y = 0.856X + 103 (r2 = 0.93). The slope (0.856) indicated that 86% of purines that reached the omasum were excreted as purine derivatives. In the two lactating cows, urinary purine derivatives accounted for 98.4% of the total purine derivatives that were excreted. Ruminal flow of microbial CP can be estimated from the CP:purine ratio of ruminal microorganisms and the excretion of purine derivatives.

Duodenal flow of microbial nitrogen estimated from urinary excretion of purine derivatives in calves after early weaning

Duodenal flow of microbial N (MN) was estimated from urinary purine derivatives to examine age-related changes in MN in male Holstein calves. In Exp. 1, endogenous purine derivatives were determined by measurement of purine derivatives in five calves fed nucleic acid-free milk replacer alone. In Exp. 2, the ratio of urinary excretion as purine derivatives to purines administered via the reticular groove was determined in three calves weaned at 5 wk of age. As a result, endogenous purine derivatives were constant at 705 mumol/(kg BW.75.d), irrespective of the amount of milk replacer, and the ratios of purine derivatives to duodenal purines were estimated to be .549, .276, .363, and .466 at wk 1, 6, 11, and 20 after weaning, respectively. Using these variables and urinary purine derivatives, the duodenal flow of MN was estimated and its relation with N balance was examined in 15 calves weaned at 5 wk of age in Exp. 3. Digestible OM was lower at wk 1 after weaning and transiently higher at wk 6. The percentage of N absorbed to N intake, N absorbed, N retained, and estimated duodenal MN were also lower at wk 1, and rapidly increased for the first 6 wk. These findings suggest that the increases in N absorbed and N retained for the first 6 wk after weaning were due to augmentation of duodenal flow of MN and dietary N that escaped ruminal degradation.

High-performance liquid chromatographic determination of (-)-beta-D-2-aminopurine dioxolane and (-)-beta-D-2-amino-6-chloropurine dioxolane, and their metabolite (-)-beta-D-dioxolane guanine in monkey serum, urine and cerebrospinal fluid

(-)-beta-D-2-Aminopurine dioxolane (APD), (-)-beta-D-2-amino-6-chloropurine dioxolane (ACPD) and dioxolane guanine (DXG) are nucleoside analogues possessing potent activity against human immunodeficiency virus (HIV) and hepatitis B virus (HBV) in vitro. APD and ACPD are metabolized in vivo to yield DXG. Reversed-phase HPLC analytical methodologies were developed for the simultaneous determination of APD and DXG, and for ACPD and DXG in monkey serum, urine and cerebrospinal fluid (CSF). 2-Fluoro-2',3'-dideoxyinosine (FDDI) served as the internal standard. The extraction recoveries of the nucleoside analogues from serum samples were similar, averaging approximately 90%. The limit of quantitation of the analytical method for serum samples was 0.1 microg/ml for DXG, and 0.25 microg/ml for APD and ACPD. The intra- and inter-day relative standard deviations for each compound at low, medium and high nucleoside concentrations were less than 9.0%. The accuracy of the assay methods was greater than 90% for prodrugs and parent compound. Similar results were observed with urine and CSF samples. Thus, these methods provide sensitive, accurate and reproducible determination of the prodrugs and parent nucleoside in biological samples.

Fast-atom bombardment mass spectrometry for mapping of endogenous methylated purine bases in urine extracts

Fast-atom bombardment (FAB) mass spectrometry, linked with tandem mass spectrometry (MS/MS), was employed for the identification of methylated purine bases in four urinary extracts of healthy subjects and fourteen urinary extracts of patients bearing colorectal tumors. In order to obtain an easy structural identification of the species present in urinary extracts, the MS/MS spectra of MH+ species of twenty nine diagnostically relevant purine bases were studied. Even if definitive quantitative data cannot be obtained by this approach, FAB mass spectra of urine extracts lead to a readily reproducible mapping of endogenous purine bases, allowing a distinction between healthy and sick subjects. Bases such as 9-ethyladenine, N6-2-isopentenyladenine and N6-benzyladenine were detected only in urine samples of colorectal tumor bearing patients. The detection in urine of compounds such as 7-methylguanine and 1-methylguanine, and their increase in the urine of colorectal tumor bearing patients, has been justified either by a more rapid turnover of nucleic acids in tumor tissue or by an increase in the extent of their methylation. The obtained results indicate that the method can be employed for diagnostic purposes.

Purine metabolism in patients with gout: the role of lead

Primary gout is characterized by increased plasma and decreased urinary concentrations of hypoxanthine, xanthine and uric acid. To examine whether lead could explain the disturbance of purine metabolism in gout, we determined hypoxanthine, xanthine and uric acid metabolism and 5-day cumulative urinary lead excretion rates after an EDTA (calcium disodium edetate) test in 27 patients with primary gout and reduced creatinine clearance (C(cr)) and in 50 patients with gout and normal C(cr). The results were compared to those obtained in 26 normal subjects matched for age. All gout patients evidenced a marked renal underexcretion of hypoxanthine, xanthine and uric acid relative to their increased plasma levels. Purine metabolism was remarkably similar in both gout groups except for a significantly lower uric acid excretion in patients with reduced C(cr). Blood lead levels and cumulative lead excretion rates were significantly higher in gout patients with renal failure as compared to patients with normal C(cr). Fourteen patients (52%) with renal insufficiency and 6 (12%) with normal C(cr) showed increased lead excretion rates (95% Cl for the difference, 29-51%, p < 0.001). Mobilizable lead was not significantly correlated with serum or urinary purine concentrations. Hypoxanthine, xanthine and uric acid underexcretion was similar in gout patients with increased or normal cumulative lead excretion rates. The prevalence of atheromatosis and arterial hypertension together was significantly higher in gout patients with renal failure than in patients with normal C(cr) (81 vs. 60%, 95% Cl for the difference, 11-31%, p < 0.005). These results indicate that lead is not a significant contributor to the renal underexcretion of purines in gout. An increased mobilizable lead is not by itself evidence that lead is the cause of the renal insufficiency in patients with primary gout. Atheromatous nephropathy and/or nephroangiosclerosis may explain impaired renal function in patients with primary gout.

Determination of rumen microbial-nitrogen production in sheep: a comparison of urinary purine excretion with methods using 15N and purine bases as markers of microbial-nitrogen entering the duodenum

The present study compares estimates of rumen microbial-N production derived from duodenal flow measurements (15N and purine bases) with those from measurements of the urinary excretion of purine derivatives. Four Rasa Aragonesa ewes fitted with simple cannulas in the rumen and proximal duodenum were used. Four diets consisting of 550 g lucerne (Medicago sativa) hay/d as sole feed or supplemented with 220, 400 and 550 g rolled barley grain/d were given in a 4 x 4 random factorial arrangement. Duodenal digesta flows were determined by the dual-phase marker technique during continuous intraruminal infusions of Co-EDTA and Yb-acetate. Microbial contribution to the non-NH3 N (NAN) flow was estimated from 15N enrichment and purines: N ratio in duodenal digesta and bacterial fractions isolated from the rumen content. Whole tract organic matter (OM) digestibility and duodenal flow of OM and NAN increased (P < 0.001) with the level of barley supplementation. Digestible OM intake ranged from 19.0 to 42.7 g/kg metabolic weight (W0.75) and the duodenal flow of purine bases and the urinary excretion of allantoin increased linearly (P < 0.001) from minimum values of 7.47 (SD 1.524) and 4.65 (SD 0.705) mmol/d respectively on the basal diet to 18.20 (SD 1.751) and 11.62 (SD 0.214) mmol/d on the 400 g barley diet; a further increase in barley supplementation decreased both variables (13.50 (SD 2.334) and 8.77 (SD 0.617) mmol/d respectively). Urinary excretion of uric acid and hypoxanthine showed a slight but significant increase (P < 0.05) over all levels of barley. Molar recoveries of duodenal purine bases as purine derivatives or allantoin in the urine were 0.78 (SD 0.156) and 0.65 (SD 0.130) respectively. The increase on barley supplementation significantly augmented microbial-N, but large differences between microbial markers employed were observed. Mean values of microbial-N estimated from the duodenal purine bases or urinary allantoin excretion were on average 18 and 29% lower than those measured by 15N.

Urinary and plasma purine derivatives in fed and fasted llamas (Lama glama and L. guanacoe)

The changes in urinary and plasma purine derivatives in response to fasting and level of feeding in llamas were examines. In one experiment, four llamas were gradually deprived of feed within 3 days and then fasted for 6 days. Daily urinary excretion of purine derivatives decreased with feed intake and leveled on the last 3 days of fasting at 177 +/- 26 mumol/kg W0.75. Allantoin and uric acid comprised 71% and 15% of total purine derivatives, respectively, in both fed and fasted states, but hypoxanthine plus xanthine increased from 9% to 36%. Plasma concentration of allantoin declined with feed intake reduction, but those of uric acid (217 mumol/l) and hypoxanthine plus xanthine (27 mumol/l) remained relatively unchanged. Concentration of uric acid was higher than that of allantoin, probably due to a high reabsorption of uric acid in renal tubules, which was measured as over 90%. In a second experiment, the four llamas were fed at 860 and 1740 g dry matter/d in a crossover design. Urinary total purine derivatives excretion responded to feed intake (10.4 vs 14.4 mmol/d), although the observed differences did not reach significance. Compared with some ruminant species, it appears that the llama resembles sheep regarding the magnitude of urinary purine derivatives excretion but is unique in maintaining a high concentration of uric acid in plasma, which could be part of the llama's adaptation to their environment.

Effect of amino acids on the excretions of purine bases and oxypurinol

To investigate whether or not amino acids affect the urinary excretion of purine bases and oxypurinol, a 12% amino acid solution was infused to 6 subjects who took allopurinol (300 mg) 6 h before the study. Amino acid infusion increased the urinary excretion and the fractional clearance of uric acid and oxypurinol and decreased the plasma concentration of oxypurinol. However, it affected neither the urinary excretion, the fractional clearance, the plasma concentration of oxypurines nor the plasma concentration of uric acid. These results indicate that amino acids affect the renal transport pathways of oxypurinol and uric acid but not those of oxypurines. In addition, it was suggested that the amino acid-induced increase in the urinary excretion of oxypurinol may be considered when allopurinol is administered to hyperuricemic patients with hypoproteinemia who have taken amino acids either orally or intravenously.

Ethanol as a xanthine dehydrogenase inhibitor

In the present study, we investigated whether ethanol inhibits the activity of xanthine dehydrogenase. Ethanol and/or inosine were administered to normal subjects, and plasma concentration and urinary excretion of purine bases were measured together with blood concentrations of lactic acid and pyruvic acid. In addition, ethanol and pyrazinamide were administered to these subjects, and plasma concentration and urinary excretion of pyrazinamide and its major metabolites were measured. Increases in plasma concentration and urinary excretion of xanthine induced by a combination of ethanol and inosine were greater than the sums of increases induced separately by ethanol and inosine, although increases in plasma concentration and urinary excretion of uric acid induced by the combination of ethanol and inosine were not different from the sums of increases induced separately by ethanol and inosine. Ethanol increased the ratio of blood lactic acid to blood pyruvic acid and decreased plasma concentration and urinary excretion of 5-hydroxypyrazinamide and 5-hydroxypyrazinoic acid. These results suggest that ethanol inhibits xanthine dehydrogenase presumably by an ethanol-induced increase in the cytosolic concentration of NADH in the liver.

Different strains of Saccharomyces cerevisiae differ in their effects on ruminal bacterial numbers in vitro and in sheep

A ruminal simulation device (Rusitec) was used to compare the effects of Saccharomyces cerevisiae strains NCYC 240, NCYC 694, NCYC 1026, NCYC 1088, and Yea-Sacc (a commercial product containing S. cerevisiae) on ruminal fermentation. S. cerevisiae NCYC 240, NCYC 1088, NCYC 1026, and NCYC 694 were grown on malt extract at 30 degrees C in aerated fed-batch culture and harvested along with spent growth medium by freeze-drying. Each vessel received daily 20 g of a basal diet consisting of hay, barley, molasses, fishmeal, and a minerals/vitamins mixture at 500, 299.5, 100, 91, and 9.5 g/kg of DM, respectively. Yeast preparations (500 mg/d) were added along with the feed. S. cerevisiae NCYC 240, NCYC 1026, and Yea-Sacc stimulated total and cellulolytic bacterial numbers, whereas S. cerevisiae NCYC 694 and NCYC 1088 had no effect on the numbers of bacteria. The effects of S. cerevisiae NCYC 240, NCYC 1026, and Yea-Sacc on ruminal fermentation were further investigated in vivo using ruminally cannulated sheep fed 1.5 kg/d of the diet used in Rusitec, supplemented with 2 g/d of yeast culture. All treatments tended to stimulate total and cellulolytic bacterial numbers. However, the stimulation was only statistically significant for S. cerevisiae NCYC 1026 with total bacterial numbers and S. cerevisiae NCYC 240 with cellulolytic bacteria (P < .05). Increased bacterial numbers were associated with an increase in the rate of straw degradation in the rumen and a nonsignificant (P > .05) increase in the excretion of purine derivatives in the urine, measured as an index of microbial nitrogen leaving the rumen.(ABSTRACT TRUNCATED AT 250 WORDS)

Gas chromatography-mass spectrometric studies of canine urinary metabolism

After the urine was treated with urease, lyophilized, and trimethylsilylated, it was examined for metabolic profiles in Dalmatian dogs and Shetland sheepdogs by gas chromatography-mass spectrometry (GC/MS), which simultaneously analyzes organic acids, amino acids, sugars, sugar alcohols, purine and pyrimidine bases, and nucleosides. The profiles were compared with those from human specimens. As clarified in past studies, Dalmatian dogs showed an extreme decrease in allantoin, which is the final product of purine metabolism in the canine of other species, and a marked detection of uric acid peak. This finding suggests that purine metabolism in Dalmatian dogs is different from that in the other species. Only two Shetland sheepdogs, whose mother had chronic renal failure, showed a marked excretion of uric acid, as in Dalmatian dogs. In addition, some Dalmatian dogs, who were maintained on a protein-restricted diet, showed a little excretion of uric acid. A large amount of uric acid is detected in combination with pentose-monosaccharides, hexose-monosaccharides and sugar alcohols in neonatal human urine in comparison with the present dog samples. A marked difference between the canine and the humans is that phenylacetylglycine, which is derived from the aromatic amino acid phenylalanine, is excreted in the canine urine. Phenylacetylglycine is not detected in the human urine, and there have been no reports of its excretion in canine urine.

Endogenous purine and pyrimidine derivative excretion in pregnant sows

The present experiment was carried out to study the endogenous losses of purine and pyrimidine derivatives from pregnant sows. Three pregnant and three non-pregnant Large White x Landrace sows were fed on a purine-free diet composed of starch, glucose, sucrose and vegetable oil, with casein as the protein source. The experiment began, for the six animals, after diagnosis of pregnancy and was divided into six 12 d periods. Urine was collected during the first 3 d of each experimental period by means of a urethral catheter for determination of allantoin, uric acid, xanthine, hypoxanthine and pseudouridine concentrations. In the absence of dietary nucleic acids (NA), allantoin and, as a consequence, excretion of total purine derivatives (PD) decreased significantly to a constant value (128.3 (SE 7.07) mumol/kg metabolic live weight (W0.75) per d), an amount assumed to represent endogenous excretion. Excretion of uric acid (38.7 (SE 2.15) mumol/kg W0.75 per d), hypoxanthine (21.0 (SE 2.58) mumol/kg W0.75 per d) and xanthine (11.2 (SE 0.83) mumol/kg W0.75 per d) were not affected by the experimental treatment, although there was a significant decrease in hypoxanthine excretion in pregnant sows (from 25.5 to 5.2 mumol/kg W0.75 per d) compared with non-pregnant sows (from 26.7 to 44.8 mumol/kg W0.75 per d). Creatinine excretion was not affected by pregnancy and was used as an internal urinary marker. Purine excretion, either expressed as mumol/kg W0.75 per d or as the ratio PD: creatinine, was not affected by experimental treatment, although an apparent increase in pseudouridine excretion, a modified unsalvageable catabolite of RNA-pyrimidine, was found in late pregnancy (3.6 v. 5.2 mol/100 mol creatinine in non-pregnant sows compared with pregnant sows at 102 d collection.

Purine metabolism in women with primary gout

PURPOSE

Uncontrolled studies have shown that women with gout have higher serum urate concentrations and similar or lower urinary uric acid excretion rates than do men with gout. These observations suggest a more defective tubular transport of uric acid in women than in men with gout. In this prospective study we assessed purine metabolism in women with primary gout under controlled conditions. We also examined whether there are sex-related differences in plasma and urinary purine concentrations among patients with primary gout.

SUBJECTS AND METHODS

Ten women with crystal-proved primary gout and normal serum creatinine levels (below 116 mmol/L) were studied while they were on a purine-restricted diet and taking no medications known to influence uric acid metabolism. For comparison, 20 men with primary gout and 10 women without gout, matched for age, race, and body mass index, were studied under the same conditions. In each subject, plasma and 24-hour urinary uric acid, hypoxanthine, and xanthine concentrations were measured. The mean of three consecutive determinations for plasma purines and five for urinary purines was used. Standard formulas were used to calculate the renal clearances and the fractional excretion of purines.

RESULTS

Mean plasma urate, hypoxanthine, and xanthine levels were significantly higher in women patients with primary gout compared with normal women (P < 0.05). Mean 24-hour urinary uric acid excretion was similar in both groups. Daily urinary hypoxanthine and xanthine excretion rates were significantly lower in gouty women patients than in control women (P < 0.05). The renal clearances and the fractional excretion of uric acid, hypoxanthine, and xanthine were markedly lower in women with primary gout than in control women (P < 0.05). Plasma and urinary purine concentrations were similarly increased and diminished, respectively, in women and men patients with primary gout. Plasma urate, hypoxanthine, and xanthine levels were inversely and significantly associated with the fractional excretion of uric acid (r = -0.520; P = 0.003), hypoxanthine (r = -0.555; P = 0.002), and xanthine (r = -0.384; P = 0.040), respectively.

CONCLUSION

Women with primary gout have markedly diminished uric acid, hypoxanthine, and xanthine excretion rates. The disturbance of purine metabolism appears to be of a similar magnitude to that observed in gouty men. The absence of significant sex-related differences in plasma and urinary purine concentrations suggests a similar tubular dysfunction for purine excretion in women and men with primary gout.

Indirect measurement of saliva secretion in sheep fed diets of different structures and the effect of such diets on ruminal fluid kinetics and fermentation pattern

Four Suffolk x Dorset sheep were allocated in a 4 x 4 Latin square design and received a hay-barley-molasses diet in one of four different physical structures: (1) pelleted; (2) pelleted:chopped (60:40); (3) chopped:pelleted (60:40); or (4) chopped. The animals were penned individually and the diet was restricted to provide 20 g of dry matter (DM) per kilogram live weight daily. The effects of the diets on rumen fluid kinetics, fermentation pattern and microbial nitrogen (MN) supply were examined. Saliva secretion was estimated using an indirect method based on water balance in the rumen. When the animals were fed the chopped diet, the salivation rate, rumen fluid volume and rumen liquid outflow were all increased significantly (P < 0.05 to P < 0.01). No consistent effect of dietary structure on rumen fluid dilution rate, purine derivative (PD) excretion or MN supply was observed. Dietary structure had no effect on the rumen fermentation pattern, digestibility of DM or nitrogen.

beta-Hydroxybutyrate decreases adenosine triphosphate degradation products in human subjects

Many disease states decrease intracellular adenosine triphosphate (ATP) levels and elevate body fluid purine levels. The use of specific metabolic substrates may reverse this process. This study was designed to test the hypothesis that beta-hydroxybutyrate, a substrate for ATP synthesis, decreases body fluid purine levels during interventions that induce ATP degradation. Decreases in these purine levels are metabolic markers for diminished ATP degradation. Two human models for stimulating ATP degradation were used to test the hypothesis. Rapid fructose infusion causes acute degradation of hepatic ATP, and ischemic exercise stimulates ATP consumption in skeletal muscle. The activity of beta-hydroxybutyrate was used in combination with phosphate, another important substrate for ATP synthesis. The studies were performed during a low-phosphate state in 10 normal subjects and during a high-phosphate state in 7 normal subjects. Metabolic variables, such as serum or urinary phosphate level, blood beta-hydroxybutyrate level, blood acetoacetate level, plasma or urinary purine level, blood lactate level, and blood ammonia level, were monitored during the study. After ischemic exercise of the forearm muscle, beta-hydroxybutyrate decreased the level of plasma total purines, blood lactate, and blood ammonia during the low-phosphate state but not during the high-phosphate state. During fructose-induced hepatic ATP breakdown, beta-hydroxybutyrate decreased late phase plasma purine increases under low-phosphate conditions only and decreased urinary total and radiolabeled purine elevations under both phosphate conditions. These data indicate that the infusion of beta-hydroxybutyrate may alter the balance from ATP degradation toward ATP resynthesis in muscle and liver by providing an immediate source of fuel and reducing equivalents under under specific metabolic conditions. This activity in combination with other metabolic interventions may have therapeutic value by restoring ATP pools in ATP-depleted tissues.

Different mass spectrometric approaches in the identification of endogenous methylated purine bases in urine extracts

A preliminary identification of endogenous and exogenous methylated purine bases in urinary extracts of healthy and tumor-bearing subjects has been performed using high performance liquid chromatography, and tandem mass spectrometry (MS/MS). MS/MS gave particularly fast and sensitive analyses, allowing the simultaneous and rapid determination of 26 different urinary methylated purines. Both sets of data confirm that tumor-bearing patients show changed levels of methylated purine bases.

Urinary excretion of purine and pyrimidine metabolites in the neonate

Random urine samples from 614 neonates were screened for metabolites of purine and pyrimidine metabolism using an adapted column chromatographic method. A restricted number of metabolites and a number of unidentified peaks appeared on the chromatograms. No inborn errors of this metabolism were found. The chromatograms were identical in term and in premature or dysmature neonates, except for the presence of more unidentified peaks in the latter group. The pattern was not influenced by the type of feeding or i.v. nutrition. Metabolites of different medications were identified. One female neonate with an increased excretion of uracil was shown to be heterozygous for ornithine carbamyl transferase deficiency.

Effect of DL-sodium lactate infusion on excretion of purine bases and oxypurinol

To investigate whether or not DL-sodium lactate inhibits the renal excretion of purine bases and oxypurinol, we administered physiological saline containing 0.2 mol DL-sodium lactate to 7 normal subjects intravenously. DL-sodium lactate infusion decreased the urinary excretion and the fractional clearance of uric acid, xanthine and oxypurinol, but the fractional clearance of hypoxanthine was not affected. These results suggested that the implications of DL-sodium lactate-induced hyperuricemia must be considered in patients with gout on its long term and high dose administration, and that the implications of DL-sodium lactate-induced prolongation of half-life of oxypurinol must be considered in hyperuricemic patients treated with allopurinol. However, since the high dose and long term administration of DL-sodium lactate is clinically rare, the effect of DL-sodium lactate infusion on the urinary excretion of uric acid, xanthine and oxypurinol may not be clinically important.

Effect of ethanol ingestion on nucleotides and glycolytic intermediates in erythrocytes and purine bases in plasma and urine: acetaldehyde-induced erythrocyte purine degradation

The effect of ethanol on nucleotides and glycolytic intermediates in erythrocytes and purine bases in plasma and urine was investigated. Ethanol ingestion (0.45 mL/kg body weight) increased plasma concentrations and urinary excretion of oxypurines (hypoxanthine and xanthine) and concentrations of adenosine monophosphate (AMP), adenosine diphosphate (ADP), and glyceraldehyde 3-phosphate+dihydroxyacetonephosphate in erythrocytes. In an in vitro incubation study using erythrocytes, acetaldehyde increased the concentrations of AMP, ADP, and glyceraldehyde 3-phosphate+dihydroxyacetonephosphate in erythrocytes as well as the concentration of hypoxanthine in the incubation medium. These results suggest that acetaldehyde (a metabolite of ethanol) induces an increase in purine degradation by erythrocytes and then contributes to the ethanol-induced enhanced purine degradation in vivo.

Xylitol-induced increase in purine degradation: a role of erythrocytes

We administered xylitol intravenously to normal subjects to investigate the mechanism of xylitol-induced increase in the purine degradation in humans. Xylitol increased the plasma concentrations of hypoxanthine, xanthine and uric acid but decreased the blood concentration of pyruvic acid. The erythrocyte concentrations of IMP, AMP, ADP, glyceraldehyde 3-phosphate and fructose 1,6-diphosphate as well as the urinary excretion of hypoxanthine and xanthine were increased, while the erythrocyte concentration of ATP was decreased. In addition, the in vitro incubation studies using erythrocytes demonstrated that both xylitol-induced purine degradation and xylitol-induced inhibition of the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate were protected by pyruvic acid. These results indicate that xylitol-induced impairment of glycolysis in erythrocytes contributes to the observed xylitol-induced increase in the purine degradation in the body.

Effect of lactate infusion on renal transport of purine bases and oxypurinol

To investigate whether or not lactic acid inhibits the renal transport of oxypurines and oxypurinol, we administered physiological saline containing 0.2 mol sodium lactate to 5 normal subjects intravenously. Lactate infusion decreased the fractional clearance of uric acid, but the fractional clearances of hypoxanthine, xanthine and oxypurinol were not affected. These results suggest that uric acid and lactic acid share the renal transport system of organic acids but hypoxanthine, xanthine and oxypurinol do not. It is further suggested that allopurinol treatment is reasonable in subjects with hyperuricemia accompanied by hyperlactatemia since only the urinary excretion of uric acid and not oxypurines (hypoxanthine and xanthine) was inhibited by lactate infusion.

Determination of creatinine and purine derivatives in ruminants' urine by reversed-phase high-performance liquid chromatography

A procedure is described for the rapid and simultaneous determination of allantoin, creatinine, uric acid, hypoxanthine and xanthine in sheep urine. Separation was achieved on a Novapak C18 column under isocratic conditions. The mobile phase was potassium phosphate buffer (10 mM, pH 4.0). A flow-rate of 0.5 ml/min, detection at 218 nm and a column temperature of 25 degrees C were employed with a total analysis time of less than 15 min. Detection limits for allantoin, creatinine, uric acid, hypoxanthine and xanthine were 1.0, 0.5, 0.5, 0.5 and 0.2 micrograms/ml, respectively, at a signal-to-noise ratio of 3 in a 20-microliters injection volume of tenfold-diluted urine. This sensitivity permits the precise determination of these compounds in ruminants' urine.