Changes in calcium oxalate crystal morphology as a function of supersaturation

Bryophyllum pinnatum (Lam.) Oken: unravelling therapeutic potential and navigating toxicity

Bryophyllum pinnatum (Lam.) Oken, a multipurpose medicinal herb, has drawn much interest for its therapeutic qualities from both traditional and modern medicine systems. Many active secondary metabolites, such as bufadienolides, triterpenes, phenols, alkaloids, glycosides, lipids, flavonoids, and organic acids, are responsible for the plant's curative properties. B. pinnatum exhibits a noteworthy significance in oncological research by exhibiting its ability to modify numerous pathways, which may suggest a potential anticancer impact. The herb is recommended for treating lithiasis, a common cause of renal failure, due to its effectiveness in dissolving stones and avoiding crystal formation. The plant has a major impact on diabetes, especially type II diabetes. Moreover, the versatility of B. pinnatum extends to its examination in connection to COVID-19. However, caution is warranted, as B. pinnatum has been reported to possess toxicity attributed to the presence of bufadienolides in its metabolic profile. A comprehensive investigation is essential to thoroughly understand and confirm the synthesis of potentially hazardous compounds. This is crucial for minimizing their presence and ensuring the safe consumption of B. pinnatum among diverse populations of organisms. This review highlights the various medical uses of B. pinnatum, including its ability to effectively treat kidney and liver diseases, as well as its anti-leishmanial, neuropharmacological, antibacterial, immunosuppressive, anti-tumour, and cytotoxic effects. While extensively employed in both traditional and scientific domains, the plant's complete medicinal potential, molecular mechanisms, safety profile, and pharmacodynamics remain ambiguous, rendering it an ideal candidate for pioneering research endeavours.

Himalayan Citrus jambhiri juice reduced renal crystallization in nephrolithiasis by possible inhibition of glycolate oxidase and matrix metalloproteinases

ETHNOPHARMACOLOGICAL RELEVANCE

Citrus fruits are a very rich source of electrolytes and citric acid. They have been used traditionally for treating urinary ailments and renal stones. Citrus jambhiri is indigenously used as a diuretic.

AIM OF THE STUDY

Present study aimed at establishing the antiurolithiatic potential of the juice of Citrus jambhiri fruits along with the elucidation of the mechanism involved in the urolithiasis disease defying activity.

METHODS

The antiurolithiatic activity was established by means of nucleation, growth and aggregation assay in the in vitro settings and by means of ethylene glycol mediated calcium oxalate urolithiasis in the male Wistar rats. Docking studies were performed in an attempt to determine the mechanism of the antiurolithiatic action.

RESULTS

Present study revealed the role of C. jambhiri fruit juice in reducing nucleation, growth and aggregation of calcium oxalate crystals by possible reduction in the urinary supersaturation relative to calcium oxalate and raising the zeta potential of the calcium oxalate crystals. C. jambhiri fruit juice treatment in experimental rats produced significant amelioration of hypercalciuria, hyperoxaluria, hyperphosphaturia, hyperproteinuria, hyperuricosuria, hypocitraturia and hypomagnesiuria and ion activity product of calcium oxalate. It exhibited nephroprotection against calcium oxalate crystals induced renal tubular dilation and renal tissue deterioration. Docking studies further revealed high binding potential of the phytoconstituents of C. jambhiri viz. narirutin, neohesperidin, hesperidin, rutin and citric acid with glycolate oxidase and matrix metalloproteinase-9.

CONCLUSION

C. jambhiri fruit juice possesses excellent antiurolithiatic activity. The study reveals antiurolithiatic mechanism that involves restoration of equilibrium between the promoters and inhibitors of stone formation; and inhibition of matrix metalloproteinases and glycolate oxidase.

An insight investigation to the antiurolithic activity of Trachyspermum ammi using the in vitro and in vivo experiments

The crude extract of Trachyspermum ammi seeds (Ta.Cr) was studied for its antiurolithic activity using the in vivo and in vitro experiments. In the in vivo experiments, Ta.Cr treatment showed a diuretic activity at the dose of 30 and 100 mg/kg and exhibited curative effect in male hyperoxaluric Wistar rats, which received 0.75% ethylene glycol (EG) in drinking water given for 3 weeks, with 1% ammonium chloride (AC) for initial three days. In the in vitro experiments, Ta.Cr delayed the slopes of nucleation and inhibited the calcium oxalate (CaOx) crystal aggregation in a concentration-dependent manner like that of potassium citrate. Ta.Cr also inhibited DPPH free radicals like standard antioxidant drug butylated hydroxytoluene (BHT), and significantly reduced cell toxicity and LDH release in Madin-Darby canine kidney (MDCK) cells, exposed to oxalate (0.5 mM) and COM (66 µg/cm²) crystals. In isolated rabbit urinary bladder strips, Ta.Cr relaxed high K⁺ (80 mM) and CCh (1 µM)-induced contractions, showing antispasmodic activity. The findings of this study suggest that the antiurolithic activity of crude extract of Trachyspermum ammi seeds may be mediated by a number of mechanisms, including a diuretic, an inhibitor of CaOx crystal aggregation, an antioxidant, renal epithelial cell protection, and an antispasmodic, thus, showing the therapeutic potential in urolithiasis, for which there is no viable non-invasive option in modern medicine.

Effects of lemon-tomato juice consumption on crystal formation in the urine of patients with calcium oxalate stones: A randomized crossover clinical trial

Background

Dietary supplementation with citrate-containing juices may serve as an effective alternative to potassium citrate therapy for preventing calcium oxalate stone recurrence. This study was performed to evaluate whether consumption of lemon-tomato juice can decrease the tendency for stone formation in the urine of calcium oxalate stone formers.

Materials and methods

The study was conducted as a prospective interventional randomized crossover clinical trial with a repeated-measures design. Twenty-two patients with calcium oxalate stones and no metabolic abnormalities in the urine treated with lithotripsy at a tertiary care center from August 2017 to July 2018 were recruited. After a 14-hour overnight fasting, urine samples were collected after the patients consumed either milk only or milk and lemon-tomato juice. Their urine was tested for multiple parameters, including urine pH, specific gravity, calcium-creatinine ratio, and supersaturation with sodium oxalate, followed by optical density measurement via spectrophotometry.

Results

There were no significant differences in the background characteristics between the 2 groups. The optical density of the urine samples obtained after consumption of milk only was significantly higher than that after consumption of milk and lemon-tomato juice (mean = 0.131 for milk only vs. 0.053 for milk and lemon-tomato juice, p < 0.001). The urine calcium-creatinine ratio was similar between the groups (mean = 0.141 for milk only vs. 0.076 for milk and lemon-tomato juice, p = 0.019).

Conclusions

The addition of lemon-tomato juice as a source of citrate in the diet significantly decreases the established risk factors for calcium oxalate stone formation in patients. This study was prospectively registered at CTRI under number CTRI/2017/04/008312 on April 7, 2017.

Antiurolithiatic Potential of Three Sri Lankan Medicinal Plants by the Inhibition of Nucleation, Growth, and Aggregation of Calcium Oxalate Crystals In Vitro

Background

Deposition and formation of stones in any part of the urinary system is called urolithiasis. CaOx is the predominant component of most stones, and the formation of these stones is a multistep process that includes supersaturation, nucleation, aggregation, growth, and retention. In ayurvedic medicine, medicinal plants are used for the management of kidney stones. The objective of this study was to determine the effect of aqueous, ethanol, and hexane extracts of Drymoglossum piloselloides leaves, Kalanchoe laciniata leaves, and Aegle marmelos flowers against CaOx urolithiasis in vitro.

Methods

The crystallization of CaOx monohydrate (COM) and dihydrate (COD) was induced in a synthetic urine system. The nucleation, growth, and aggregation of crystals were measured using spectrophotometric methods. The results were compared against the polyherbal drug, Cystone, under identical concentrations. Crystals generated in the urine were also observed under light microscopy. Statistical differences and percentage inhibitions were calculated using standard formulae and compared. A preliminary phytochemical screening was also performed to detect active phytoconstituents present in the three plants used in the study.

Results

The results obtained clearly demonstrated that Kalanchoe laciniata, Aegle marmelos, and Drymoglossum piloselloides have the capacity to inhibit the nucleation, growth, and aggregation of CaOx crystals. Microscopic examination of crystals revealed the presence of more COM than COD crystals but a dose-dependent reduction in crystals was observed in the presence of plant extracts. Hexane, ethanol, and aqueous extracts of all three plants had different capabilities to inhibit nucleation, growth, and aggregation of CaOx crystals but their activities were different at different concentrations. Preliminary phytochemical screening revealed the presence of reducing sugars, proteins, flavonoids, tannins, and polyphenol compound in Kalanchoe laciniata and Drymoglossum piloselloides and reducing sugars, proteins, anthracene glycosides, and saponins in Aegle marmelos.

Conclusions

This study provided evidence that Kalanchoe laciniata, Aegle marmelos, and Drymoglossum piloselloides have the potential to be developed as inhibitors of nucleation, growth, and aggregation of CaOx crystals in the treatment of urolithiasis.

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

The removal of kidney stones can lead to small residual fragments remaining in the human body. Residual stone fragments can act as seeds for kidney stone crystallization and may necessitate another intervention. Therefore, it is important to create a consistent model with a particle size comparable to the range of kidney stone fragments. Thus, the size-determining parameters such as supersaturation ratio, energy input, and pH value are examined. The batch crystallizations were performed with supersaturation ratios between 5.07 and 6.12. The compositions of the dried samples were analyzed with Raman spectroscopy, infrared spectroscopy, and X-ray diffraction (XRD). The samples were identified as calcium oxalate monohydrate with spectroscopic analysis, while calcium oxalate dihydrate being the most prominent crystalline species at all supersaturation ratios for the investigated conditions. The aggregate size, obtained with analytical centrifugation, varied between 2.9 and 4.3 μm, while the crystallite domain size, obtained from XRD, varied from 40 to 61 nm. Our results indicate that particle sizes increase with increasing supersaturation, energy input, and pH. All syntheses yield a high particle heterogeneity and represent an ideal basis for reference materials of small kidney stone fragments. These results will help better understand and control the crystallization of calcium oxalate and the aggregation of such pseudopolymorphs.

Effect of calcium content of diet on crystal formation in urine of patients with calcium oxalate stones: a randomized crossover clinical trial

Background

Patients with idiopathic calcium oxalate stones are advised to consume a low-oxalate diet to prevent recurrence. In this study, on patients with calcium oxalate stones we have attempted to determine the effect of calcium content of diet on the formation of calcium oxalate crystals in urine by in vitro supersaturation study of fresh postprandial urine samples and observing the morphology of the crystals formed using polarized optical microscopy.

Methods

The trial was conducted as a prospective interventional randomised crossover clinical trial in a repeated measures design. Sixty patients with calcium oxalate stones and no metabolic abnormalities in urine treated by lithotripsy at a tertiary care centre during the period May 2016 to May 2019 were recruited. Following a 14 h overnight fasting, urine samples were collected after providing the patient with either a low- or high-calcium meal for breakfast followed four hours later, by high-oxalate meal for lunch. Urine was tested for multiple parameters including urine pH, specific gravity, calcium/creatinine ratio and supersaturation of urine with sodium oxalate followed by optical density measurement by spectrophotometry and microscopic analysis of crystals formed.

Results

Optical density values and calcium/creatinine ratio of urine samples obtained after high-calcium meal are significantly higher than in corresponding sample obtained after low-calcium meal (p < 0.001). These findings were reflected in the morphology of formed crystals in their size, shape and number. When urinary calcium levels were low, no crystals were formed during supersaturation study of postprandial urine samples following a high-oxalate diet.

Conclusions

High calcium content in diet significantly contributes to kidney stone formation. There is a lower risk of kidney stone formation with a low-calcium meal even on consumption of a high-oxalate diet.

Differential bound proteins and adhesive capabilities of calcium oxalate monohydrate crystals with various sizes

Adhesion of calcium oxalate (CaOx) crystals onto renal tubular epithelial cells is one of the critical steps in kidney stone formation. However, effects of crystal size on the crystal adhesive capability remained unclear. This study compared the adhesive capabilities of CaOx monohydrate (COM) crystals with various sizes (<10 μm, 20-30 μm, 50-60 μm, and > 80 μm). Crystal-cell adhesion assay showed size-dependent increase of COM crystal adhesion onto epithelial cell surface using the larger crystals. Identification of apical membrane proteins that could bind to COM crystals by tandem mass spectrometry (nanoLC-ESI-ETD MS/MS) demonstrated size-specific sets of the COM crystal-binding proteins. Among these, numbers of known oxalate-binding proteins and COM crystal receptors were greatest in the set of the largest size (>80 μm). Atomic force microscopy (AFM) revealed that adhesive forces between carboxylic-immobilized AFM tip and COM crystal surface and between COM-mounted AFM tip and renal epithelial cell surface were size-dependent (greater for the larger crystals). In summary, the adhesive capability of COM crystals is size-dependent - the larger the greater adhesive capability. These data may help better understanding of the pathogenic mechanisms of kidney stone formation at an initial stage when renal tubular cells are exposed to various sizes of COM crystals.

Raman chemical imaging, a new tool in kidney stone structure analysis: Case-study and comparison to Fourier Transform Infrared spectroscopy

BACKGROUND AND OBJECTIVES

The kidney stone's structure might provide clinical information in addition to the stone composition. The Raman chemical imaging is a technology used for the production of two-dimension maps of the constituents' distribution in samples. We aimed at determining the use of Raman chemical imaging in urinary stone analysis.

MATERIAL AND METHODS

Fourteen calculi were analyzed by Raman chemical imaging using a confocal Raman microspectrophotometer. They were selected according to their heterogeneous composition and morphology. Raman chemical imaging was performed on the whole section of stones. Once acquired, the data were baseline corrected and analyzed by MCR-ALS. Results were then compared to the spectra obtained by Fourier Transform Infrared spectroscopy.

RESULTS

Raman chemical imaging succeeded in identifying almost all the chemical components of each sample, including monohydrate and dihydrate calcium oxalate, anhydrous and dihydrate uric acid, apatite, struvite, brushite, and rare chemicals like whitlockite, ammonium urate and drugs. However, proteins couldn't be detected because of the huge autofluorescence background and the small concentration of these poor Raman scatterers. Carbapatite and calcium oxalate were correctly detected even when they represented less than 5 percent of the whole stones. Moreover, Raman chemical imaging provided the distribution of components within the stones: nuclei were accurately identified, as well as thin layers of other components. Conversion of dihydrate to monohydrate calcium oxalate was correctly observed in the centre of one sample. The calcium oxalate monohydrate had different Raman spectra according to its localization.

CONCLUSION

Raman chemical imaging showed a good accuracy in comparison with infrared spectroscopy in identifying components of kidney stones. This analysis was also useful in determining the organization of components within stones, which help locating constituents in low quantity, such as nuclei. However, this analysis is time-consuming, making it more suitable for research studies rather than routine analysis.

In vitro and in vivo models for the study of urolithiasis

Preclinical animal research has greatly contributed and will continue to contribute in our understanding of various disease states and provided methods for more understanding of disease states and designs to test novel pharmaco-therapeutic interventions against these diseases. For urolithiasis, scientists have developed numerous in vitro and in vivo models that attempt to replicate human urolithiasis. In this review, I have explained in vitro and in vivo models that are more common, affordable, and easy to replicate. In the in vitro models, I have focused on the CaOx crystallization models and in the in vivo models, hyperoxaluric rat model has been explained along with other available option such as Knockout (KO) mice and fly models. Each model has been explained stepwise along with its pros and cons.

Methanol and ethylene glycol intoxication

Accidental or intentional ingestion of substances containing methanol and ethylene glycol can result in death, and some survivors are left with blindness, renal dysfunction, and chronic brain injury. However, even in large ingestions, a favorable outcome is possible if the patient arrives at the hospital early enough and the poisoning is identified and appropriately treated in a timely manner. This review covers the common circumstances of exposure, the involved toxic mechanisms, and the clinical manifestations, laboratory findings, and treatment of methanol and ethylene glycol intoxication.

Nephrectomy as a cause of chronic kidney disease in the treatment of urolithiasis: a case-control study

OBJECTIVE

To analyze the clinical course of nephrectomized patients due to complications related to nephrolithiasis and ascertain the prevalence of chronic kidney disease (CKD) in this population.

METHODS

From 2005 to 2010, 658 patients were treated with urolithiasis. Among these, 30 (4.6%) were nephrectomized. For each case, a control was selected and matched to the case by age, sex and disease duration. All data were collected from medical records, which contained the clinical, laboratory evaluation and diagnostic imaging.

RESULTS

Age of the study group was 51.5 ± 10.4 years and the control group 47.1 ± 5.2 years. There were 17 (85%) women and three men in each group. Patients from the study group reported 3 (range, 1-5) episodes of acute renal colic before nephrectomy. Urinary tract infection and hematuria was detected in 70% of cases before surgery. In addition, half of the patients had at least one previous urological procedure. The control group showed higher urinary levels of calcium (216.1 ± 114.3 vs. 130.9 ± 72.2), uric acid (530.2 ± 197.4 vs. 424 ± 75.2) and citrate (755 ± 533 vs. 380.2 ± 260.7), p < 0.01, 0.03 and 0.01, respectively. The creatinine clearance was lower in the study group, 52.5 ± 18.8 ml/min vs. 92.9 ± 24.2 ml/min in the control group (p < 0.001).

CONCLUSIONS

There was a decrease in kidney function in nephrectomized patients compared to a control group of stone-forming patients with both kidneys. Prospective studies are needed to assess the incidence of CKD in patients with nephrolithiasis submitted to nephrectomy.

Antiurolithic activity of Origanum vulgare is mediated through multiple pathways

Background

Origanum vulgare Linn has traditionally been used in the treatment of urolithiasis. Therefore, we investigated the crude extract of Origanum vulgare for possible antiurolithic effect, to rationalize its medicinal use.

Methods

The crude aqueous-methanolic extract of Origanum vulgare (Ov.Cr) was studied using the in vitro and in vivo methods. In the in vitro experiments, supersaturated solution of calcium and oxalate, kidney epithelial cell lines (MDCK) and urinary bladder of rabbits were used, whereas, in the in vivo studies, rat model of urolithiasis was used for the study of preventive and curative effect.

Results

In the in vitro experiments, Ov.Cr exhibited a concentration-dependent (0.25-4 mg/ml) inhibitory effect on the slope of nucleation and aggregation and also decreased the number of calcium oxalate monohydrate crystals (COM) produced in calcium oxalate metastable solutions. It also showed concentration-dependent antioxidant effect against DPPH free radical and lipid peroxidation induced in rat kidney tissue homogenate. Ov.Cr reduced the cell toxicity using MTT assay and LDH release in renal epithelial cells (MDCK) exposed to oxalate (0.5 mM) and COM (66 μg/cm²) crystals. Ov.Cr relaxed high K⁺ (80 mM) induced contraction in rabbit urinary bladder strips, and shifted the calcium concentration-response curves (CRCs) towards right with suppression of the maximum response similar to that of verapamil, a standard calcium channel blocker. In male Wistar rats receiving lithogenic treatment comprising of 0.75% ethylene glycol in drinking water given for 3 weeks along with ammonium chloride (NH₄Cl) for the first 5 days, Ov.Cr treatment (10-30 mg/kg) prevented as well as reversed toxic changes including loss of body weight, polyurea, crystalluria, oxaluria, raised serum urea and creatinine levels and crystal deposition in kidneys compared to their respective controls.

Conclusion

These data indicating the antiurolithic activity in Ov.Cr, possibly mediated through inhibition of CaOx crystallization, antioxidant, renal epithelial cell protective and antispasmodic activities, rationalizes its medicinal use in urolithiasis.

The initial and subsequent inflammatory events during calcium oxalate lithiasis

BACKGROUND

Crystallization is believed to be the initiation step of urolithiasis, even though it is unknown where inside the nephron the first crystal nucleation occurs.

METHODS

Direct nucleation of calcium oxalate and subsequent events including crystal retention, cellular damage, endocytosis, and hyaluronan (HA) expression, were tested in a two-compartment culture system with intact human proximal tubular HK-2 cell monolayer.

RESULTS

Calcium oxalate dihydrate (COD) was nucleated and bound onto the apical surface of the HK-2 cells under hypercalciuric and hyperoxaluric conditions. These cells displayed mild cellular damage and internalized some of the adhered crystals within 18h post-COD-exposure, as revealed by electron microscopy. Prolonged incubation in complete medium caused significant damage to disrupt the monolayer integrity. Furthermore, hyaluronan disaccharides were detected in the harvested media, and were associated with HAS-3 mRNA expression.

CONCLUSION

Human proximal cells were able to internalize COD crystals which nucleated directly onto the apical surface, subsequently triggering cellular damage and HAS-3 specific hyaluronan synthesis as an inflammatory response. The proximal tubule cells here demonstrate that it plays an important role in facilitating urolithiasis via endocytosis and creating an inflammatory environment whereby free hyaluronan in tubular fluid can act as crystal-binding molecule at the later segments of distal and collecting tubules.

Sensitivity and specificity of 24-hour urine chemistry levels for detecting elevated calcium oxalate and calcium phosphate supersaturation

OBJECTIVES

The gold standard for determining likelihood of calcium oxalate (CaOx) and calcium phosphate (CaPhos) stone formation in urine is supersaturation of CaOx and CaPhos. Our objective was to investigate whether traditional measurement of total calcium, oxalate and phosphate in a 24-hour urine collection is sufficiently sensitive and specific for detecting elevated supersaturation to preclude the more expensive supersaturation test.

METHODS

We performed a retrospective review of 150 consecutive patients with nephrolithiasis who underwent measurement of CaOx supersaturation (CaOxSS) and CaPhos supersaturation (CaPhosSS), as well as total calcium, oxalate and phosphate in a 24-hour urine collection. We used various cut-off values to determine sensitivity and specificity of 24-hour urine measurements for detecting elevated CaOxSS and CaPhosSS.

RESULTS

In men and women, the sensitivity of 24-hour calcium for detecting elevated CaOxSS was 71% and 79%, respectively; for oxalate, sensitivity was 59% and 36%, respectively. In men and women, the sensitivity of 24-hour calcium for detecting elevated CaPhosSS was 74% and 88%, respectively; for phosphate, sensitivity was 57% and 8%, respectively. In men and women, the specificity of 24-hour calcium for detecting elevated CaOxSS was 55% and 48%, respectively; it was 60% for detecting elevated CaPhosSS in both men and women.

CONCLUSION

Traditional 24-hour urine analysis is sensitive, but not specific, for detecting elevated CaOxSS and CaPhosSS. Most patients with abnormal 24-hour urine analysis have normal supersaturation, and treatment decisions based on traditional urine analysis would lead to overtreatment in these patients.

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.

Physico-chemical alterations of urine in experimental hyperoxaluria: a biochemical approach with fucoidan

Urinary supersaturation-induced crystal formation has been attributed as one of the key factor for the pathogenesis/progression of lithogenesis. This study was aimed at investigating whether fucoidan, a naturally occurring sulfated glycosaminoglycan, could ameliorate the biochemical changes in urine induced by stone formation. Two groups of male albino Wistar rats (120+/-20 g) received 0.75% ethylene glycol (EG) for 28 days to induce hyperoxaluria, and one of them received sulfated polysaccharides (fucoidan from Fucus vesiculosus, 5 mg kg(-1), s.c.), commencing from the 8(th) day of the experimental period. One group was maintained as normal control group and another group served as drug control, which received sulfated polysaccharides. The urine collected from all the groups was analysed for changes in pH, volume, oxalate, calcium, phosphorus, uric acid, magnesium, citric acid and glycosaminoglycans. Urinary crystals were analysed with a light microscope. Renal tissues were studied under polarized light for deposition of crystals and also analysed for their oxalate and calcium content. The changes in extracellular matrix on crystal deposition were also evaluated. The urinary pH and volume were altered in rats treated with EG along with an increase in weight of the kidney. Further, administration of EG to rats increased the supersaturation of urine by escalating the levels of the stone-forming constituents, such as oxalate, calcium, phosphorus and uric acid, which was completely restored by fucoidan treatment. The decrease in the inhibitors, like citrate, magnesium and glycosaminoglycans, in urine was prevented by the co-treatment with fucoidan. In hyperoxaluric rats, there was an increased excretion of calcium oxalate monohydrate crystals in urine along with crystal deposition in renal tissues; this was prevented by fucoidan treatment. Fucoidan administration reversed even the tissue levels of calcium and oxalate. The increased accumulation of collagen and expression of transforming growth factor-beta(1) in hyperoxaluria was normalized on fucoidan administration. These results suggest that the physico-chemical alterations in urine produced during hyperoxaluria can be reversed by fucoidan administration.

Defective urinary crystallization inhibition and urinary stone formation

INTRODUCTION

Nephrocalcin (NC) is a glycoprotein produced in the kidney and inhibits calcium oxalate crystal formation. It has been separated into 4 isoforms (A, B, C, and D) and found that (A + B) are more abundant than (C + D) in urine of healthy subjects, but the reverse is seen in human urine of kidney stone patients. To further examine the role of this protein in inhibition of urinary crystallization, nephrocalcin isoforms were purified from 2 genetically pure dog species.

MATERIALS AND METHODS

We studied healthy Beagles, known to be non-stone forming dogs, and Mini-Schnauzers, known to be calcium oxalate stone formers. NC was isolated and purified from each group. Urinary biochemistry and calcium oxalate crystal growth inhibition were measured.

RESULTS

Specific crystal growth inhibition activity was significantly higher in non-stone forming dogs (9.79 +/- 2.25 in Beagles vs. 2.75 +/- 1.34 of Mini-Schnauzers, p < 0.005). Dissociation constants toward calcium oxalate monohydrate were 10-fold different, with Beagles' isoforms being 10 times stronger inhibitors compare to those of Mini-Schnauzers'. Isoforms C + D of NC were the main isoforms isolated in stone-forming dogs.

CONCLUSION

NC of these two species of dogs differently affects calcium oxalate crystallization and might have a role in determining ulterior urinary stone formation.