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PubMed1983

Quantification of urinary oxalate with oxalate oxidase from beet stems.

We describe an automated (ABA-100) enzymic method for determination of urinary oxalate by use of oxalate oxidase (EC 1.2.3.4) isolated from beet stems. The H2O2 produced by the oxidation of oxalate by oxalate oxidase is measured by coupling with oxidation and conjugation of 3-methyl-3-benzothiazolinone hydrazone with N,N-dimethylaniline with catalysis by horseradish peroxidase. The resulting indamine dye is measured spectrophotometrically by the difference in absorption at 500 and 600 nm. Interfering substances are removed by oxidation with acidic ferric chloride and by cation-exchange chromatography. The assay is sensitive to 5 mg of urinary oxalate per liter, the standard curve is linear to 70 mg/L, and the procedure requires less than 3 h for completion. The within-run CV was less than 1.6%, the between-day CV less than 5.6%. The oxalate oxidase method results in a mean and reference interval for oxalate excretion that are comparable with those by isotope dilution, gas-chromatographic, colorimetric, and other enzymic procedures.

Autoanalysis↗
PubMed1994

Assay of plasma oxalate with soluble oxalate oxidase.

We use oxalate oxidase from barley seedlings for the colorimetric determination of oxalate in plasma. The oxalate is converted to hydrogen peroxide, which, in the presence of peroxidase, is detected by a Trinder-like chromogenic system. Optimization of the assay, including deproteinization and elimination of interferences from reducing substrates, is described. Ascorbate additions (200 mumol/L) did not affect oxalate concentration in plasma, even after long frozen storage. Mean analytical recovery of oxalate averaged 102% +/- 6.9%, imprecision (CV) at 2.0 mumol/L was 7.2%, and the lower limit of quantification (CV = 20%) was 0.6 mumol/L. Results correlated well with those by chromatography (r = 0.999, Sy/x = 0.29 mumol/L, n = 32, range for x, y = 0-140 mumol/L). Plasma oxalate concentrations measured in 32 healthy subjects ranged from 0.6 to 2.9 mumol/L (mean 1.28, SD 0.71 mumol/L), which agrees with those measurable by using indirect radioisotopic dilution methods. Patients with primary hyperoxaluria and chronic renal failure exhibited markedly greater plasma concentrations of oxalate.

Adolescent↗
PubMed2004

Calcium oxalate monohydrate binding protein: a diagnostic biomarker for calcium oxalate kidney stone formers.

Urinary oxalate is a biomarker for calcium oxalate kidney stone disease; however, its assay is insensitive and nonspecific. Calcium oxalate monohydrate (COM) binding protein (45 kDa) is a promoter of calcium oxalate kidney disease, which is markedly upregulated by oxalate induced oxidative stress. The current study was carried out to evaluate whether COM binding protein can serve as a diagnostic marker for calcium oxalate kidney stone formers. COM binding protein was isolated, purified and antibody was raised against it in rabbits. Urine samples (24 h) were collected from patients suffering from various kidney diseases such as acute nephritis, chronic nephritis, nephrotic syndrome, calcium oxalate (CaOx) stone formers, uric acid stone formers, struvite stone formers and calcium phosphate stone formers. This COM binding protein was quantified by an in house ELISA method and the excretion was found to lie between 2 and 3 mg in control samples, while in CaOx stone formers it was detected between 11 and 19 mg. Urinary risk factors were assayed. We conclude that COM binding protein can serve as a diagnostic marker for CaOx stone formers.

Animals↗
PubMed1995

Calcium oxalate crystalluria in elderly patients and treatment with naftidrofuryl oxalate.

Crystalluria is important in the evaluation of patients with urinary stone and is more frequently encountered in elderly than in younger adults. After noting that calcium oxalate monohydrate crystalluria was higher in elderly patients, we undertook a study to determine if oral treatment with naftidrofuryl oxalate, a drug frequently prescribed for elderly patients in France, was associated with crystalluria. The presence of early morning crystalluria was assessed in non-stone-forming patients hospitalized in a geriatric department. We studied 251 patients without a history of nephrolithiasis (mean age; 81.6 +/- 8.5 years) of whom 49 had been treated orally with naftidrofuryl oxalate at a mean dosage of 485 +/- 120 mg/24h. We identified and quantified the crystals in one early morning urine sample kept at room temperature. The frequency of crystalluria in elderly patients without stones who were not taking naftidrofuryl oxalate was 31.7% compared with only 6% in the general adult population. In this group, mainly calcium phosphate crystals were found. In patients who received naftidrofuryl oxalate, the frequency of crystalluria was 51% of which the major component was calcium oxalate monohydrate and not calcium phosphate. Naftidrofuryl oxalate may enhance crystal formation in elderly patients. This should be taken into account, particularly when other predisposing factors for nephrolithiasis are present, and a preventive increase in fluid intake considered.

Administration, Oral↗
PubMed1999

Short-chain acyl-CoA-dependent production of oxalate from oxaloacetate by Burkholderia glumae, a plant pathogen which causes grain rot and seedling rot of rice via the oxalate production.

In Burkholderia glumae (formerly named Pseudomonas glumae), isolated as the causal agent of grain rot and seedling rot of rice, oxalate was produced from oxaloacetate in the presence of short-chain acyl-CoA such as acetyl-CoA and propionyl-CoA. Upon purification, the enzyme responsible was separated into two fractions (tentatively named fractions II and III), both of which were required for the acyl-CoA-dependent production of oxalate. In conjugation with the oxalate production from oxaloacetate catalyzed by fractions II and III, acetyl-CoA used as the acyl-CoA substrate was consumed and equivalent amounts of CoASH and acetoacetate were formed. The isotope incorporation pattern indicated that the two carbon atoms of oxalate are both derived from oxaloacetate, and among the four carbon atoms of acetoacetate two are from oxaloacetate and two from acetyl-CoA. When the reaction was carried out with fraction II alone, a decrease in acetyl-CoA and an equivalent level of net utilization of oxaloacetate were observed without appreciable formation of CoASH, acetoacetate or oxalate. It appears that in the oxalate production from oxaloacetate and acetyl-CoA, fraction II catalyzes condensation of the two substrates to form an intermediate which is split into oxalate and acetoacetate by fraction III being accompanied by the release of CoASH.

Acetyl Coenzyme A↗
PubMed1967

Plasma oxalic acid and calcium levels in oxalate poisoning.

Observations are reported on five cases of suicide or attempted suicide by poisoning with oxalic acid or ethylene glycol. Elevated oxalic acid levels were observed in the plasma, stomach contents, and a number of tissues. Raised oxalic acid levels in plasma were associated with reduced total and ultrafilterable calcium levels. It is suggested that the reduction in plasma total calcium level is due mainly to the deposition of calcium oxalate in the soft tissues, but inhibition of the parathyroid glands may be a contributory factor. Microscopic examination of various tissues indicated that oxalic acid is deposited in the tissues in two forms: (1) crystalline calcium oxalate dihydrate in the kidney and (2) a non-crystalline complex of calcium oxalate and lipid in liver and other tissues.

Adult↗
PubMed1980

Oxalate urolithiasis: significance of serum and urinary oxalate.

With a new enzymatic test using oxalate oxidase, serum and urinary oxalate can easily and quickly be determined. Serum oxalate in females was significantly higher than in males (39.5 mumol/l, 30.8 mumol/l). Increased serum levels were found only in male patients. Urinary excretion did not reveal sex-dependent differences in healthy persons. The normal range of oxalate excretion in 104 adult healthy persons was 83-365 mumol/day (95% quartile). In 130 stone formers (nonrecurrent and recurrent group) urinary oxalate excretion was found to be in the normal range. Evaluation of urinary oxalate concentration in morning samples showed increased levels in both groups of male stone formers. Oxalate concentration was unaltered in female patients.

Adult↗
PubMed2000

The effect of rumen adaptation to oxalic acid on selection of oxalic-acid-rich plants by goats.

Rumen microbial degradation is an important route for detoxification of secondary plant compounds encountered in the diets of free-grazing ruminants. Exposure to diets containing particular secondary plant compounds can lead to increased rates of secondary compound degradation in the rumen. An experiment was conducted to determine whether rumen adaptation to oxalic acid would influence the diet selection of goats offered choices between plant species differing in their oxalic acid content. Twelve adult female goats were divided into two groups of six animals each. One group received a daily oral dose, in gelatin capsules, of 0.6 mmol oxalic acid/kg live weight per d throughout the experiment while the other group received placebos consisting of empty gelatin capsules. After an adaptation period of 8 d, the animals were allowed to graze a mixture of spinach (rich in oxalic acid) and cabbage (low in oxalic acid) for 7 h/d on two consecutive days per week during four consecutive 1-week periods. Intervening days were spent on grass pasture. Diet composition and intake were measured using cuticular wax n-alkanes as internal markers. Results showed that adapted goats included a higher proportion of spinach in their diet (P < 0.05) although absolute intakes of spinach were the same for the two groups. Goats in the oxalic-acid-adapted group consumed less cabbage than control animals (P < 0.05) suggesting that adaptation to oxalic acid at the rumen level may have interfered with detoxification of cabbage-derived secondary plant compounds. Voluntary intake increased progressively through the four experimental periods (P < 0.001) with a tendency for higher intakes among control than among adapted animals (P < 0.1). The experiment demonstrates how differences in the rate of degradation of secondary plant compounds may influence diet selection in ruminants.

Adaptation, Physiological↗
PubMed1997

Calcium phosphate/calcium oxalate crystal association in urinary stones: implications for heterogeneous nucleation of calcium oxalate.

PURPOSE: Most stones contain more than one type of crystals, and some combinations, such as calcium phosphate/calcium oxalate, are more common than others. Epitaxy between the crystals has been suggested to play a role in growth of such stones. The specific aim of this study is to investigate the involvement of calcium phosphate in crystallization of calcium oxalate. MATERIALS AND METHODS: Twenty calcium oxalate stones or stone fragments were examined using various microscopic techniques, including scanning, transmission and back-scattered electron microscopy. Similarly, calcium oxalate stones induced on a plastic foreign body implanted inside urinary bladders of laboratory rats were also investigated. Examination of the interface between calcium phosphate and calcium oxalate crystals was emphasized. RESULTS: Close association between crystals of calcium phosphate and calcium oxalate were found in both the human and rat stones. All crystals examined were associated with an organic matrix on the surface and contained copious amounts of organic material within the crystalline entities. Interface between the crystals also appeared to be occupied by organic matrix. CONCLUSIONS: Results of this and other studies from our laboratory indicate that epitaxy between various crystals, even though theoretically possible, appears unlikely in vivo. The appearance of specific crystalline combinations in stones is probably a result of the urinary environment being conducive for crystallization of those components. Heterogeneous nucleation of calcium oxalate is most probably induced by biological elements, including membranous cellular degradation products.

Animals↗
PubMed1997

Investigation with chitosan-oxalate oxidase-catalase conjugate for degrading oxalate from hyperoxaluric rat chyme.

Enteric hyperoxaluria manifests due to hyperabsorption of dietary oxalate, secondary to a variety of chronic gastrointestinal disorders. The potential use of chitosan immobilized oxalate oxidase-catalase conjugate to deplete the oxalate content of food materials, while they are in the digestive tract has been evaluated by treating rat stomach chyme with such an enzyme preparation. Oxalate oxidase, obtained from beet stem, was adsorbed on chitosan along with catalase and then cross linked with glutaraldehyde to stabilize the derivative. This chemical modification of oxalate oxidase brought about a shift in its optimal pH from 4.2 to 3.8 with a marginal increase in its K(m). Compared to native enzyme, the modified oxalate oxidase exhibited increased storage stability, higher thermal stability and enhanced resistance to proteolytic digestion and heavy metal inactivation. These improved properties of the immobilized oxalate oxidase possibly render it suitable for oral administration under hyperoxaluric conditions.

Animals↗
PubMed1987

[Resorption of oxalic acid in calcium oxalate nephrolithiasis].

In 43 healthy reference persons and 54 patients with relapsing calcium oxalate nephrolithiasis the absorption of oxalic acid was measured by means of 14C-oxalic acid. In patients with oxalate calculi the absorption of oxalic acid is totally increased and also in such ones with Whewellite-calculi. It is decreased in carriers of Weddelite calculi. The increase of the absorption of oxalic acid in patients with mixed calculi is not significant.

Adult↗
PubMed1984

Raised transmembrane oxalate flux in red blood cells in idiopathic calcium oxalate nephrolithiasis.

Red-blood-cell transmembrane oxalate flux was measured in a group of patients with idiopathic calcium oxalate nephrolithiasis and in normal controls. The mean transmembrane oxalate flux rate was significantly higher in stone-forming patients than in controls (0.93 +/- SD 0.31/min vs 0.29 +/- 0.11/min). 80% of stone-forming patients showed raised (greater than 2SD above the mean in controls) transmembrane oxalate flux. Anomalous cellular oxalate transport may be an important pathogenetic factor in calcium oxalate nephrolithiasis.

Adult↗
PubMed2005

Citrate provides protection against oxalate and calcium oxalate crystal induced oxidative damage to renal epithelium.

PURPOSE: Oxalate and calcium oxalate (CaOx) crystals are injurious to renal epithelial cells. The injury is caused by the production of reactive oxygen species (ROS). Citrate is a well-known inhibitor of CaOx crystallization and as such it is one of the major therapeutic agents prescribed. Since citrate increases cellular reduced nicotinamide adenine dinucleotide phosphate and glutathione (GSH), we hypothesized that exogenously administered citrate should act as an antioxidant and protect cells from oxalate induced injury. MATERIALS AND METHODS: We exposed LLC-PK1 and MDCK cells to 500 microM/ml oxalate or 150 mug/cm calcium oxalate crystals for 30, 60 and 180 minutes with or without 3 mg/ml citrate in the medium. We determined cell viability by lactate dehydrogenase release and trypan blue exclusion, ROS involvement by changes in hydrogen peroxide and GSH, and lipid peroxidation by quantifying 8-isoprostane. RESULTS: The presence of citrate was associated with significant decrease in lactate dehydrogenase release (p <0.001) and staining with trypan blue (p <0.05). In addition, there was a significant increase in GSH (p <0.005) and a decrease in the production of hydrogen peroxide (p <0.05) and 8-isoprostane (p <0.0005) secretion into the culture medium when citrate was present in the medium. CONCLUSIONS: Citrate protects cells from oxalate and CaOx crystal induced injury by preventing lipid peroxidation through a decrease in ROS production. The results provide additional data for the beneficial role of citrate therapy for CaOx nephrolithiasis.

Calcium Oxalate↗
PubMed2005

Effects of urine dilution on quantity, size and aggregation of calcium oxalate crystals induced in vitro by an oxalate load.

Increasing urinary volume is an important tool in the prevention of calcium renal stones. However, the mechanism of how it actually works is only partially understood. This study aimed at assessing how urine dilution affects urinary calcium oxalate crystallization. A total of 16 male idiopathic calcium oxalate (CaOx) stone-formers and 12 normal male subjects were studied and 4 h urine samples were taken twice, under low (undiluted urine) and high hydration conditions (diluted urine). An equal oxalate load (1.3 mmol/L) was added to both types of urine and the crystallization parameters were assessed. In both stone-formers and normal subjects, the crystallization processes were significantly (p<0.05 or less) more marked in the undiluted urine than in the diluted urine in terms of: a) total quantity of calcium oxalate dihydrate (COD) and calcium oxalate monohydrate (COM) crystals; b) total quantity of crystalline aggregates; and c) aggregation index (i.e., ratio between the area occupied by crystalline aggregates and the area occupied by all the crystals present). The comparison between stone-formers and normal subjects showed that the greatest difference was for the size of COD crystals, which were larger in the urine of the stone-formers. A further important finding was an inverse relationship between changes in urinary volume and in the aggregation index (r = -0.53, p = 0.004). In conclusion, urine dilution considerably reduces crystallization phenomena induced in vitro by an oxalate load in both calcium stone-formers and normal subjects.

Adult↗
PubMed1979

Electron paramagnetic resonance study of iron oxalate in calcium oxalate renal stones.

Weak electron paramagnetic resonance (EPR) signals from a number of calcium oxalate renal stones are attributed to an iron oxalate component. The g-value of the resonance is 2.0036 and its width is approximately 9 gauss. The EPR resonance from stones has the same characteristics as resonances from iron introduced into calcium oxalate and oxalic acid as an impurity. A sharp increase in EPR signal when calcium oxalate renal stones are exposed to intense light is attributable to the reduction of Fe3+ and the formation of the oxalate radical ion (C2O4)-.

Calcium Oxalate↗
PubMed1975

Oxalate accumulation from citrate by Aspergillus niger. I. Biosynthesis of oxalate from its ultimate precursor.

Carbon-14 was incorporated from citrate-1,5-14C, glyoxylate-14C(U), or glyoxylate-1-14C into oxalate by cultures of Aspergillus niger pregrown on a medium with glucose as the sole source of carbon. Glyoxylate-14C(U) was superior to glyoxylate-1-14C and citrate-1,5-14C as a source of incorporation. By addition of a great amount of citrate the accumulation of oxalate was accelerated and its maximum yield increased. In a cell-free extract from mycelium forming oxalate from citrate the enzyme oxaloacetate hydrolase (EC3.7.1.1) was identified. Its in vitro activity per flask exceeded the rate of in vivo accumulation of oxalate. Glyoxylate oxidizing enzymes (glycolate oxidase, EC1.1.3.1; glyoxylate oxidase, EC1.2.3.5;NAD(P)-dependent glyoxylate dehydrogenase; glyoxylate dehydrogenase, CoA-oxalylating, EC1.2.1.7) could not be detected in cell-free extracts. It is concluded that in cultures accumulating oxalate from citrate after pregrowth on glucose, oxalate arises by hydrolytic cleavage of oxaloacetate but not by oxidation of glyoxylate.

Aspergillus↗
PubMed1975

Colorimetric determination of urinary oxalate recovered as calcium oxalate. Application of a simple correction factor for incomplete preciptation.

A method is described for determination of oxalate in urine. Prior to the determination the oxalate is first precipitated from the urine as calcium oxalate. Correction for incomplete precipitation can be made by applying one simple correction formula. The extent of this correction has been established by determination of the recovery of added [14-C] oxalate. The determination of the precipitated oxalate was carried out by an automated version of the colorimetric reaction of oxalate with uranium and 4-(2-pyridylazo)-resorcinol as originally described by Neas, R.E. and Guyon, J.C. in 1972 (Anal. Chem. 44, 799-805).

Autoanalysis↗
PubMed2004

Fractional magnesium absorption is significantly lower in human subjects from a meal served with an oxalate-rich vegetable, spinach, as compared with a meal served with kale, a vegetable with a low oxalate content.

The aim of the present study was to evaluate Mg absorption from a test meal served with an oxalate-rich vegetable, spinach, as compared with a test meal served with a vegetable with a low oxalate content, kale. Mg absorption was measured by a stable-isotope technique based on extrinsic labelling of the test meals and faecal monitoring of the excreted isotope labels. Nine healthy adults participated in the study. The test meals were based on 100 g phytate-free white bread, served with 300 g spinach (6.6 mmol oxalate; 0.7 mmol (25)Mg label added, 5.0 mmol total Mg) or 300 g kale (0.1 mmol oxalate; 1.2 mmol (26)Mg label added, 4.8 mmol total Mg). The test meals were served on days 1 and 3, at breakfast and lunch, using a cross-over design. The results from the present study demonstrated that apparent Mg absorption was significantly lower from the meal served with spinach (26.7 (sd 10.4) %) than the meal served with kale (36.5 (sd 11.8) %) (P=0.01). However, the lower fractional apparent Mg absorption from the test meal served with spinach can be assumed to be, at least partly, counterbalanced by the higher native Mg content of spinach as compared with kale. Although based on indirect evidence, i.e. not based on an evaluation of added (or removed) oxalic acid, the difference in Mg absorption observed in the present study is attributed to the difference in oxalic acid content between the two vegetables.

Adult↗