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PubMed1986

Successful treatment of hyperuricosuric calcium oxalate nephrolithiasis with potassium citrate.

Calcium stone (renal) formation in patients with hyperuricosuria has been ascribed to the urate-induced crystallization of calcium oxalate. Citrate (0.5mM), added to synthetic medium metastably supersaturated with respect to calcium oxalate, was shown to inhibit heterogeneous nucleation of calcium oxalate by monosodium urate (2 mg/mL). Long-term trial with potassium citrate (60 to 80 mEq/day) was therefore undertaken to determine whether induced hypercitraturia would prevent calcium oxalate stone formation in 19 patients with hyperuricosuria. The treatment produced a sustained rise in urinary pH by 0.55 to 0.85 to the high normal range (6.5 to 7.0). Urinary citrate levels rose by 249 to 402 mg/day to approximate the normal mean value of 643 mg/day. Commensurate with these changes, urinary saturation of calcium oxalate (relative saturation ratio) and the amount of undissociated uric acid declined significantly. However, the urinary uric acid and saturation of monosodium urate remained elevated. Stone formation declined from 1.55 +/- 2.70 per patient-year to 0.38 +/- 1.22 per patient-year during mean treatment period of 2.35 +/- 0.88 years. Stones ceased to form in 16 of 19 patients during treatment. The results provide physicochemical and clinical evidence for the utility of potassium citrate in the management of hyperuricosuric calcium oxalate nephrolithiasis.

Adult↗
PubMed2002

An investigation of calcium citrate-malate as a calcium source for young broiler chicks.

Two experiments were conducted to compare a sample of calcium citrate-malate (CC-M) with a sample of commercial-grade limestone in starting broiler chick diets. In the first experiment, with 0.7 or 0.9% calcium from limestone or CC-M, no differences in bone development (dry fat-free tibia, tibia weight, tibia ash, or tibia calcium) were observed due to calcium source. However, chicks fed the diets based on CC-M had better 0- to 18-d body weight gains and feed conversion ratios than those fed limestone. In the second experiment with 0.50, 0.55, 0.60, 0.65, or 0.70% calcium from limestone or CC-M, chicks again had better body weight gains when fed CC-M compared to those fed limestone. Chicks fed diets based on CC-M and NaP2PO4 had very similar bone development and tibial dyschondroplasia pathology to those fed limestone and Na2H2PO4. However, a control group of chicks fed 0.70% calcium from limestone and dicalcium phosphate did not grow as well as the others and had lower weights of tibia and tibial bone ash, calcium, and phosphorus compared to the others. It is concluded that CC-M is a good calcium source, comparable in bioavailability to limestone. Although CC-M may improve broiler growth, its action is not through increased bioavailability of calcium.

Animal Nutritional Physiological Phenomena↗
PubMed2005

New device and method for flux-proportional sampling of mobile solutes in soil and groundwater.

The importance of monitoring the transport of organic contaminants in soil and groundwater, and the pros and cons of existing sampling methods, are outlined. A new, alternative sampling method is proposed, using a passive sampler that functions as a water-permeable, semi-infinite sink for passing solutes of interest. Tracers integrated in the device store information on the volume of water passing through the sampler during the installation period. The conceptual basis of the sampling method is described. This device enables flux-proportional monitoring of the concentrations of mobile contaminants in the soil and groundwater. 14C-labeled phenanthrene (PHEN) and glyphosate (GLY) are used as case study compounds in laboratory experiments. The sorption capacities and uptake kinetics of 13 adsorbents are screened and compared, as well as the dissolution kinetics of three tracer salts: calcium citrate, calcium fluoride (CaF2), and calcium hydrogen phosphate (CaHPO4). The application of the passive sampler is then demonstrated in long-term laboratory experiments, using large soil columns under steady-state hydraulic conditions. The accumulated flux of PHEN was sampled with an accuracy of 3.6%-17.8%, using graphitized carbon, hexagonal mesoporous silica, and cross-linked polymers as adsorbents. The accumulated flux of GLY was sampled with an accuracy of 12.4%, using gamma-alumina as an adsorbent. The advantages and limitations of this new environmental monitoring method are discussed.

Adsorption↗
PubMed2006

Insulin resistance and low urinary citrate excretion in calcium stone formers.

Epidemiological data suggest an association between kidney stones and some features of metabolic syndrome such as an overweight condition, arterial hypertension or glucose intolerance. However, mechanisms remain to be elucidated. This study aimed to evaluate insulin resistance, as assessed by homeostasis model assessment (HOMA-IR), and urine composition analysis in patients affected by calcium nephrolithiasis. A cohort of 61 (38 male, 29-57 years of age) non-diabetic calcium stone formers was studied. Data about body mass index, arterial blood pressure, serum biochemistry including parathyroid hormone and calcitriol were recorded in all the patients; fasting glucose and insulin were determined to calculate HOMA-IR value and accordingly the patients were grouped into tertiles. Urine pH and urinary excretion of calcium, citrate, phosphate, oxalate, uric acid, urea and creatinine were measured on 24h urine samples. Patients of the highest HOMA-IR tertile showed lower urine citrate levels than patients of the lowest HOMA-IR tertile (475+/-243 vs. 630+/-187 mg/24h, p<0.05), whereas no difference was detected as far as urinary oxalate, calcium, uric acid, phosphate, and urine pH and urine volume output were concerned. HOMA-IR values were positively related to uric acid serum levels (r=0.31, p<0.05) and negatively to urinary citrate excretion (r=-0.26, p<0.05). Hypocitraturic patients showed higher levels of HOMA-IR than normocitraturic ones (3.03+/-0.92 vs. 2.25+/-1.19, p<0.05). This study shows that a higher level of insulin resistance is associated with lower urinary citrate excretion, and that hypocitraturic patients show a greater insulin resistance than normocitraturic calcium stone formers. This may be related to changes in citrate, Na(+)-K(+) and H(+) renal tubule transports, which have been described in insulin resistance. In conclusion, insulin resistance may contribute to an increased risk of calcium stone formation by lowering urinary citrate excretion. This finding suggests the need for a careful metabolic assessment in patients known to form calcium stones in order to ensure stone recurrence prevention and cardiovascular protection.

Adult↗
PubMed2004

Molecular modulation of calcium oxalate crystallization by osteopontin and citrate.

Calcium oxalate monohydrate (COM), which plays a functional role in plant physiology, is a source of chronic human disease, forming the major inorganic component of kidney stones. Understanding molecular mechanisms of biological control over COM crystallization is central to development of effective stone disease therapies and can help define general strategies for synthesizing biologically inspired materials. To date, research on COM modification by proteins and small molecules has not resolved the molecular-scale control mechanisms. Moreover, because proteins directing COM inhibition have been identified and sequenced, they provide a basis for general physiochemical investigations of biomineralization. Here, we report molecular-scale views of COM modulation by two urinary constituents, the protein osteopontin and citrate, a common therapeutic agent. Combining force microscopy with molecular modeling, we show that each controls growth habit and kinetics by pinning step motion on different faces through specific interactions in which both size and structure determine the effectiveness. Moreover, the results suggest potential for additive effects of simultaneous action by both modifiers to inhibit the overall growth of the crystal and demonstrate the utility of combining molecular imaging and modeling tools for understanding events underlying aberrant crystallization in disease.

Calcium Oxalate↗