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At least 811 records · Page 45Linked to original sources
PubMed1994

Effect of calcium supplement preparation containing small amounts of citrate on the absorption of aluminium in normal subjects and in renal failure patients.

It is well known that Al absorption is markedly enhanced by citrate. The aim of the study was to document whether low-dose citrate ingestion (4 g/day) contained in a well-known effervescent calcium supplement was sufficient to increase Al absorption in 16 normal volunteers and 15 subjects with stable chronic renal failure under conditions of either Ca carbonate or Al hydroxide supplementation. Serum and urine Al levels were measured using flameless atomic absorption spectrophotometry as previously described. After Ca carbonate plus Ca citrate ingestion, there was no rise over baseline (Ca Carbonate alone) serum or urine Al levels in either group. Ca carbonate and Al hydroxide taken together produced a significant rise in serum and urine Al levels in both groups. Maintaing Al hydroxide but substituting Ca citrate for the carbonate (same dose of elemental Ca) produced a further significant increment in serum Al (0.47 +/- 0.28-1.15 +/- 0.8 mumol/l; p < 0.001) and in urine Al(1.37 +/- 0.46-5.77 +/- 5.21 mumol/l; p < 0.001) in the chronic renal failure group as well as in serum Al (0.42 +/- 0.2-0.76 +/- 0.48 mumol/l; p < 0.001) and urine Al (2.70 +/- 1.24-8.24 +/- 3.96 mumol/l; p < 0.001 in the normal volunteer group. Due to decreased urine excretion, the increment in serum Al in the CRF group was significantly greater than in the normal subjects (p < 0.02). Thus small quantities of citrate present in effervescing Ca supplements can significantly enhance intestinal Al absorption even in normal subjects. All citrate-containing preparations are totally contra-indicated in chronic renal failure patients ingesting Al-containing compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1981

Aconitase activity, citrate oxidation, and zinc inhibition in rat ventral prostate.

Aconitase activity and citrate oxidation were determined in mitochondrial preparations from rat ventral prostate. Aconitase activity in prostate mitochondria was approximately 10% of the activity observed in kidney preparations. The prostate aconitase activity was completely inhibited by the addition of 1.0 mmol/l zinc and kidney aconitase was inhibited by approximately 50%. The presence of 1.0 mmol/l zinc also markedly inhibited the formation of isocitrate from cis-aconitate. The reduction of NADP by citrate was markedly inhibited (approx. 95%) by 1.0 mmol/l zinc as compared with a 70 and 40% inhibition of aconitate--and isocitrate--stimulated reduction, respectively. These results indicate that zinc might be a strong inhibitor of aconitase activity with an inhibitory effect on isocitrate dehydrogenase also. The effect of 1.0 mmol/l zinc on citrate oxidation was studied by determining 14CO2 production from 6-14C-citrate. 14CO2 was significantly inhibited by zinc. These results further corroborate the conclusion that citrate accumulation in prostate might be the result of limited citrate oxidation which results from a combination of low aconitase activity and possibly zinc inhibition.

Aconitate Hydratase↗
PubMed1988

Net citrate production by isolated prostate epithelial cells.

The net production of citrate from exogenous substrates by rat ventral prostate was investigated. The preparation of isolated prostate epithelial cells was described. These cells were capable of oxidizing pyruvate (5 mmol/l) as a source of acetyl coenzyme A. The addition of aspartate + alpha-ketoglutarate (5 mmol/l) in the presence of pyruvate resulted in significant net production of citrate and excess oxalacetate. In the presence of aspartate and glutamate, the cells were capable of producing citrate without excessive oxalacetate production. Neither glucose alone nor glucose plus pyruvate resulted in net citrate production. The results demonstrated that aspartate could serve as a 4-carbon source of oxalacetate for citrate synthesis. Furthermore, the results indicate the intramitochondrial operation of a glutamate-aspartate-citrate pathway involving mitochondrial aspartate aminotransferase and glutamic dehydrogenase activities in prostate epithelial cells.

Acetyl Coenzyme A↗
PubMed1987

Influence of thyroid hormone deficiency on the citrate synthase activity in rat brain regions during early postnatal development.

The developmental pattern of citrate synthase activity has been studied in the liver and several brain areas of hypothyroid rats during the 4 first weeks of life. While citrate synthase activity in the liver showed a rise during the 2 first weeks of life, different patterns of enzyme activity were found in the brain regions of euthyroid animals. Citrate synthase activity increased in the cerebellum, decreased in the cerebral cortex and did not change significantly in the brain stem during the period studied. In the liver and brain areas, too, a decrease in citrate synthase activity was observed during hypothyroidism. From the 2nd week of birth, the citrate synthase activity in the brain but not in the liver was found to have recovered. The newly elevated citrate synthase activity coincided with a slight increase in thyroid hormone serum levels.

Animals↗
PubMed1989

Urinary citrate excretion in patients with urolithiasis and normal subjects.

Citrate is a normal constituent of urine which combines with calcium to form a soluble salt. Urinary citrate excretion was examined in patients with urolithiasis and normal subjects by a specific enzymatic technique. There was a considerable overlap in the urinary citrate excretion between normal subjects and stone-formers, but the citrate-creatinine ratio, the citrate-calcium ratio and the citrate-magnesium-calcium ratio, which were all highly significantly lower (p less than 0.001) in stone-formers than in controls, proved most reliable in discriminating between these groups.

Calcium↗
PubMed1991

Value of routine citrate analysis and calcium/citrate ratio in calcium urolithiasis.

24-hour urinary citrate excretion was measured in 176 calcium oxalate stone formers and 100 normal controls. A statistically significant difference (p less than 0.03) could be found between the two groups. When stone formers were divided into a group of 69 patients with recurrent calcium urolithiasis (RCU) and a group of 106 patients with a single stone episode, the latter did not differ from the control group, while in RCU a significantly lower citrate excretion compared with controls (p less than 0.005) could be found. Thus, patients with RCU could benefit from alkali citrate prophylaxis. A female-male difference in citrate excretion could not be found in either the control group or stone formers. Recurrent stone formers presented a significantly higher calcium/citrate ratio compared with controls, which would indicate an increased risk for stone formation. The value of routine citrate analysis is limited, however, by the great, variability of citrate levels in stone formers and controls.

Adult↗
PubMed1985

Calcium citrate: reduced propensity for the crystallization of calcium oxalate in urine resulting from induced hypercalciuria of calcium supplementation.

The effect of calcium citrate (800 mg calcium/day in 4 divided doses) on urinary biochemistry and crystallization of calcium salts was examined in 18 normal subjects. During treatment, urinary calcium increased significantly (from 150 +/- 65 (SD) to 248 +/- 77 mg/day). Urinary citrate rose from 611 +/- 208 to 730 +/- 225 mg/day, owing largely to the alkali load. The urinary saturation of calcium oxalate rose by only 41% during calcium citrate treatment, due mainly to citrate complexation of calcium (rather than by 62% without such complexation). Moreover, the formation product of calcium oxalate rose during treatment, indicating that the enhanced citrate excretion augmented the inhibitor activity against calcium oxalate crystallization. Thus, calcium citrate may not be attendant with the risk for stone formation usually associated with calcium supplementation.

Adult↗
PubMed1996

Reduction of granulocyte activation during hemodialysis with regional citrate anticoagulation: dissociation of complement activation and neutropenia from neutrophil degranulation.

Neutropenia and degranulation of neutrophils during hemodialysis with cellulosic membranes have been linked to complement activation, whereas in the synthetic polymethyl methacrylate (PMMA) membrane, degranulation occurs without notable complement activation. The mechanisms of neutrophil degranulation under these conditions have not yet been elucidated. Ionized calcium is an important prerequisite of granulocyte activation during in vitro blood contact with both types of artificial surfaces. This study compared the effect of normal ionized calcium during heparin anticoagulation with the effect of extracorporeal calcium depletion during regional citrate anticoagulation on activation of blood components. Because ionized calcium is reduced only in the extra-corporeal circuit, citrate anticoagulation in addition helps to differentiate between extracorporeal and systemic activation phenomena. Twelve chronic hemodialysis patients were dialyzed with polymethyl methacrylate (PMMA, 16 treatments) or cuprophane (CUP, 16 treatments) membranes either during regional citrate anticoagulation or while anticoagulated with heparin. During hemodialysis with CUP, anticoagulation with citrate significantly reduced neutropenia, C3a levels, and lactoferrin release. Elastase concentrations, however, were not reduced by citrate, probably because elastase release occurred not locally in the cuprophane dialyzer, but mostly in the systemic circulation of the patient. PMMA did not elevate C3a levels, and neutropenia was only mild. Both parameters were not influenced by citrate anti-coagulation. However, PMMA profoundly induced elastase and lactoferrin release during heparin anti-coagulation. Depletion of ionized calcium markedly reduced PMMA-mediated neutrophil degranulation in the extracorporeal circuit. The results indicate that ionized calcium is a requirement for neutrophil degranulation during hemodialysis. In PMMA membranes, neutrophil degranulation occurs independent of high complement levels, occurs at least partially inside the dialyzer, and requires the presence of ionized calcium in the extracorporeal circuit. In cuprophane membranes, degranulation was uncoupled from neutropenia and did not correlate with the degree of complement activation. Even in cuprophane dialysis, degranulation of secondary granules was markedly dependent on ionized calcium levels in the extracorporeal circuit.

Anticoagulants↗
PubMed2001

Caffeine citrate: a review of its use in apnoea of prematurity.

UNLABELLED: Apnoea of prematurity is a common condition in neonates born at less than 37 weeks' gestational age; it affects approximately 90% of premature neonates weighing under 1000 g at birth, and 25% of infants with a birthweight of less than 2500 g. Caffeine, a methylxanthine which occurs naturally in many plants, has been used for over 20 years to treat apnoea of prematurity. In a recent double-blind, placebo-controlled trial, apnoea was eliminated or reduced by at least 50% in significantly more neonates receiving caffeine citrate as first-line treatment than those receiving placebo. In a nonblind trial, caffeine citrate was more effective at reducing apnoeic episodes when compared with neonates receiving no treatment. Caffeine as first-line treatment demonstrated similar efficacy to theophylline or aminophylline (theophylline ethylenediamine) in 4 small randomised studies. Caffeine citrate was generally well tolerated in short term clinical trials, with very few adverse events reported. Caffeine was associated with fewer adverse events than theophylline in randomised trials. No differences in the incidence of individual adverse events were reported between caffeine citrate and placebo in a double-blind, randomised trial. Long term tolerability data are not yet available. CONCLUSIONS: Caffeine citrate was generally well tolerated by neonates in clinical trials and it decreased the incidence of apnoea of prematurity compared with placebo. It has demonstrated similar efficacy to theophylline, but is generally better tolerated and has a wider therapeutic index. Caffeine citrate should, therefore, be considered the drug of choice when pharmacological treatment of apnoea of prematurity is required.

Apnea↗
PubMed1990

Influence of aluminum citrate and citric acid on mineral metabolism in wether sheep.

A 60-d trial was conducted to determine effects of Al citrate and citric acid on DM digestibility (DMD) and metabolism of Mg, Ca, P, K, Na and Al. Eighteen crossbred, yearling wether lambs equipped with ruminal cannulas were fed a basal diet containing .12% Mg and 2.87% K (DM basis) and were allotted to three treatments: 1) control, 2) 2,000 ppm Al as Al citrate and 3) citric acid equivalent to the citrate in treatment 2. Treatments were administered in 200 ml of deionized water twice daily in divided doses via ruminal cannula. Balance trials were conducted during d 0 to 5, 6 to 10, 25 to 35 and 50 to 60. Dry matter digestibility decreased (P less than .05) approximately 3 percentage units in lambs receiving Al. Treatment with Al citrate increased (P less than .01) apparent absorption and retention of Al compared to those receiving citric acid alone. Approximately 30% of ingested and infused Al was apparently absorbed. Compared to citric acid, Al citrate treatment lowered apparent absorption and retention of Mg and Ca during d 0 to 5. Apparent Ca absorption and retention again were lowered during d 50 to 60. Urinary Ca was increased (P less than .01) and apparent P absorption (P less than .10) and retention (P less than .05) were decreased by Al citrate during all measurement periods. Apparent absorption of K decreased (P less than .05) slightly in response to Al treatment. Apparent absorption of Na was not influenced by Al treatment. Serum Mg and P decreased and serum Ca increased in response to Al treatment. Results demonstrate negative effects of ingested Al, but not of citric acid, on DMD and metabolism of Mg, Ca, P and K.

Absorption↗
PubMed1991

Influence of aluminum-citrate and citric acid on tissue mineral composition in wether sheep.

A 60-d trial was conducted to determine effects of A1-citrate and citric acid on tissue mineral composition in wether lambs. Eighteen crossbred, yearling wether lambs equipped with ruminal cannulas were fed a diet containing low (.12%) Mg and high (2.87%) K (DM basis) and were allotted to three treatments: 1) control; 2) 2,000 micrograms A1 as A1-citrate/g of diet DM and 3) citric acid equivalent to the citrate in treatment 2. Treatments were administered in 200 ml of deionized water twice daily in divided doses via ruminal cannula. At the end of 60 d, wethers were slaughtered and samples of rib and tibia bone, liver, kidney, brain, spleen, pancreas, parathyroid and pituitary gland were analyzed for mineral concentration. Concentrations of A1 increased (P less than .05) in rib, tibia, liver, kidney, spleen and pituitary gland and tended to increase in brain (P less than .13) in wethers treated with A1-citrate compared to citric acid. Magnesium was decreased in rib (P less than .01) and tended to be decreased in pituitary gland (P less than .15), whereas Ca tended to be decreased in pancreas (P less than .07), kidney (P less than .11) and parathyroid (P less than .10) by A1-citrate treatment compared to citric acid. Potassium decreased (P less than .01) in liver, Fe increased (P less than .05) in kidney, Zn decreased in pituitary (P less than .05) and tended to decrease in pancreas (P less than .10) due to A1-citrate but not citric acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1980

Effect of acidosis, alkalosis and monofluoroacetate administration on citrate and ATP content of rat renal medulla and papilla.

1. --Renal distribution of citrate showed that there is an increase in citrate content from cortex to medulla and a decrease from medulla to papilla. Alkalosis produced an increase in citrate content and acidosis a decrease in renal citrate content, in each of the studied renal area. Monofluoroacetate produced no significant change in citrate content of medulla or papilla; it did not interfere with the acido-basic related changes in cortex citrate content, but its effect was additive. 2. --Renal distribution of ATP significantly decreased from cortex to medulla and from medulla to papilla. Acid or basic diet had no influence on intratissular ATP content. Fluoroacetate decreased renal ATP content.

Acidosis↗
PubMed2001

ATP-citrate lyase from the green sulfur bacterium Chlorobium limicola is a heteromeric enzyme composed of two distinct gene products.

The reductive tricarboxylic acid cycle functions as a carbon dioxide fixation pathway in the green sulfur bacterium, Chlorobium limicola. ATP-citrate lyase, one of the key enzymes of this cycle, was partially purified from C. limicola strain M1 and the N-terminal sequence of a 65-kDa protein was found to show similarity toward eukaryotic ATP-citrate lyase. A DNA fragment was amplified with primers designed from this sequence and an internal sequence highly conserved among eukaryotic enzymes. Using this fragment as a probe, we isolated a DNA fragment containing two adjacent open reading frames, aclB (1197 bp) and aclA (1827 bp), whose products showed significant similarity to the N- and C-terminal regions of the human enzyme, respectively. Heterologous expression of these genes in Escherichia coli showed that both gene products were essential for ATP-citrate lyase activity. The recombinant enzyme was purified from the cell-free extract of E. coli harboring aclBA for further characterization. The molecular mass of the recombinant enzyme was determined to be approximately 532--557 kDa by gel-filtration. The enzyme catalyzed the cleavage of citrate in an ATP(-), CoA- and Mg(2+)-dependent manner, where ATP and Mg(2+) could be replaced by dATP and Mn(2+), respectively. ADP and oxaloacetate inhibited the reaction. These properties suggested that ATP-citrate lyase from C. limicola controlled the cycle flux depending on intracellular energy conditions. This paper provides the first direct evidence that a bacterial ATP-citrate lyase is a heteromeric enzyme, distinct from mammalian enzymes.

ATP Citrate (pro-S)-Lyase↗
PubMed2002

Prevention of spinal bone loss by potassium citrate in cases of calcium urolithiasis.

PURPOSE: We determine if potassium citrate treatment stabilizes spinal bone density among patients with recurrent calcium oxalate nephrolithiasis. MATERIALS AND METHODS: We studied a group of 16 men and 5 women with stones taking potassium citrate from 11 to 120 months. They represented all patients from the Stone Clinic who took potassium citrate alone for at least 11 months. L2-L4 bone mineral density data before and after potassium citrate treatment were retrieved retrospectively and analyzed. RESULTS: In the combined group L2-L4 bone mineral density increased significantly by 3.1% over mean duration of 44 months. Z score, corrected for age matched normal values, increased significantly by 3.8%. Urinary pH, citrate and potassium increased significantly during treatment but urinary calcium did not change. CONCLUSIONS: Potassium citrate, a commonly used drug for the prevention of recurrent nephrolithiasis, may avert age dependent bone loss. Spinal bone density increased in most patients when it normally decreases.

Adult↗
PubMed1991

Effect of vitamin D deficiency on D-glucose and citrate transport in rat renal basolateral membrane vesicles.

We had previously reported that feeding rats on Steenbock and Black's rickets-inducing diet markedly influences the metabolic picture of the kidney and the transmembrane transport systems of D-glucose and citrate in renal brush-border membrane vesicles. We have now studied D-glucose and citrate transport into basolateral membrane vesicles prepared from kidney cortex of control and rachitic rats and the effect of 1,25-dihydroxyvitamin D3 on these transport systems was also investigated. D-glucose and citrate uptake, determined in the presence of a Na(+)-gradient, was lowered in rachitic animals and 1,25-dihydroxyvitamin D3 administration proved to be ineffective in restoring normal values. Citrate transport, determined in the presence of a K(+)-gradient, was not influenced by both rickets and 1,25-dihydroxyvitamin D3 supply. The in vitro addition to vesicle preparations of calcium or phosphate or citrate or 1,25-dihydroxyvitamin D3 did not show a selective influence on D-glucose and citrate uptake.

Animals↗
PubMed1990

Altered contractile response in neonatal myocardium to citrate-phosphate-dextrose infusion.

The clinical use of citrate-phosphate-dextrose during blood-product transfusion is known to affect ionized calcium levels and can result in depression of myocardial contractility. The immature heart appears to have an intrinsic reduction in contractile state compared with the adult heart and may be more dependent on transsarcolemmal calcium flux for regulation of contraction. The myocardial contractile response to citrate infusion was compared in neonatal and adult rabbit hearts using clinically comparable citrate-phosphate-dextrose concentrations. Isovolumic left ventricular pressures were monitored in an isolated, crystalloid-perfused heart model before, during, and after 15 minutes of citrate-phosphate-dextrose infusion. Developed pressure decreased 42.1 +/- 4.9% from control within 1 minute in the neonatal group versus 24.3 +/- 4.3% in the adult group (p less than 0.02). The effect on diastolic function was paradoxical in the neonate with a 43.1 +/- 11.9% increase in end-diastolic pressure compared with a 9.7 +/- 7.8% decrease in the adult (p less than 0.01). These results indicate that the neonatal heart appears more sensitive to the myocardial effects of citrate infusion with impairment of both systolic and diastolic function. The decreased ventricular compliance in the neonate with citrate-phosphate-dextrose suggests that the myocardial effects may not be simply due to changes in ionized calcium concentration.

Animals↗
PubMed1990

Rat ATP citrate-lyase. Molecular cloning and sequence analysis of a full-length cDNA and mRNA abundance as a function of diet, organ, and age.

ATP citrate-lyase is the primary enzyme responsible for the synthesis of cytosolic acetyl-CoA in many tissues. We have isolated a full-length cDNA copy of 4.3 kilobase pairs encoding the ATP-citrate lyase mRNA by screening rat liver cDNA library using oligonucleotide probes designed from peptide sequences obtained from the purified rat enzyme. Expression of this cDNA in bacteria, followed by immunoblotting with antibody directed against the ATP citrate-lyase, further demonstrated the identity of this clone. Nucleic acid sequence data indicate that the cDNA contains the complete coding region for the enzyme, which is 1100 amino acids in length with a calculated molecular weight of 121,293. RNA blot analysis indicated an mRNA species of about 4.3 kilobase pairs in livers of chow-fed rats. Rats maintained on low fat, high carbohydrate diets exhibited a striking increase (50-fold) in the level of liver ATP citrate-lyase mRNA as compared with the control animals maintained on a normal diet. The tissue distribution of this mRNA in chow-fed animals revealed a relatively high abundance of the message in liver and adrenal, moderate levels were found in lung, brain, and large intestine with only trace amounts of the message in small intestine, stomach, testis, spleen, pancreas, kidney, and heart. During rat development, the ATP citrate-lyase mRNA was relatively high in the liver at parturition, followed by a reduction in its level during suckling. Higher amounts of the mRNA were detected again in adult animals. The isolation and characterization of the mRNA for ATP citrate-lyase will allow further studies on the reaction mechanism and metabolic regulation of this key enzyme in lipogenesis and cholesterogenesis.

ATP Citrate (pro-S)-Lyase↗
PubMed1989

[Analysis of urinary citrate and oxalate in 42 diabetics].

Among 42 diabetics, there were 32 with the disease remaining uncontrolled after treatment. Their fasting blood glucose was 15.24 +/- 5.37 mmol/L (mean +/- S), urinary glucose 42.6 +/- 47.83 g/24 hr, urinary oxalate 0.43 +/- 0.16 mmol/24 hr and urinary citrate 3.60 +/- 2.28 mmol/24 hr All of these levels were higher than those in a control group (P less than 0.001). Urinary citrate level was significantly positively correlated with fasting blood glucose level (gamma = 0.3954, P less than 0.001). In the remaining 10 diabetics with the disease controlled after treatment the fasting blood glucose was 7.04 +/- 0.92 mmol/L, urinary citrate 1.92 +/- 0.96 mmol/24 hr and urinary oxalate 0.37 +/- 0.11 mmol/24 hr. All of these levels were significantly lower than those before treatment (P less than 0.01) and were not different from those in the control group (P greater than 0.05). This explains that urinary citrate and oxalate increased when diabetes is uncontrolled as a result of accelerated decomposition due to increased metabolism. Urinary oxalate level is correlated positively with that of urinary citrate (gamma = 0.3773, P less than 0.05). Urinary oxalate and citrate are good index reflecting diabetic metabolic changes. Analysis of urinary oxalate with ion-chromatography is accurate and rapid method worthy to be used clinically.

Adult↗