Crystallisation of ammonium acid urate and other uric acid derivatives from urine.
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Acetaldehyde↗
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Nitric oxide inhibits prooxidant actions of uric acid during copper-mediated LDL oxidation.
Interactions between uric acid and physiologically relevant fluxes of nitric oxide ((?)NO) during copper-mediated low-density lipoprotein (LDL) oxidation were evaluated. In the absence of (?)NO, a dual pro- and antioxidant action of uric acid was evident: low concentrations of uric acid enhanced lipid oxidation and alpha-tocopherol consumption, while its protective role was observed at higher concentrations. The prooxidant effects of uric acid were mostly related to its copper-reducing ability to form Cu(+), an initiator of lipid oxidation processes. While the prooxidant action of uric acid was completely inhibited by (?)NO, the antioxidant action of (?)NO was slightly counterbalanced by uric acid. Enhancement of alpha-tocopherol consumption by uric acid was inhibited in the presence of (?)NO while additive antioxidant effects between (?)NO and uric acid were observed in conditions where uric acid spared alpha-tocopherol. Altogether, these results suggest that in the artery wall, the (?)NO/uric acid pair may exert antioxidant actions on LDL, even if increased amounts of redox active copper were available at conditions favoring prooxidant activities of uric acid.
Alkenes↗
Uric acid calculi: types, etiology and mechanisms of formation.
The study of the composition and structure of 41 stones composed of uric acid was complemented by in vitro investigation of the crystallization of uric acid. Uric acid dihydrate (UAD) precipitates from synthetic urine under physiological conditions when the medium is supersaturated with respect to this compound, though uric acid anhydrous (UAA) represents the thermodynamically stable form. Solid UAD in contact with liquid transforms into UAA within 2 days. This transition is accompanied by development of hexagonal bulky crystals of UAA and appearance of cracks in the UAD crystals. Uric acid calculi can be classified into two groups, differing in outer appearance and inner structure. Type I includes stones with a little central core and a compact columnar UAA shell and stones with interior structured in alternating densely non-columnar layers developed around a central core; both of them are formed mainly by crystalline growth at low uric acid supersaturation. Type II includes porous stones without inner structure and stones formed by a well developed outermost layer with an inner central cavity; this type of stones is formed mainly by sedimentation of uric acid crystals generated at higher uric acid supersaturation.
Chemical Phenomena↗
The relationship between Achilles tendon rupture and serum uric acid level.
The serum uric acid level of 30 patients with a rupture of the Achilles tendon was compared with that of 30 healthy control subjects matched for age and sex. In patients with a ruptured Achilles tendon the serum uric acid level was significantly higher than in the control subjects. This finding was not dependent on sex or race. It is possible that hyperuricaemia is a contributing factor in rupture of the Achilles tendon and warrants further study. It is suggested that this finding might be related to an adverse effect on the tendon's nutrition.
Achilles Tendon↗
Effect of azlocillin on uric acid levels in serum.
Uric acid levels in serum were observed to fall precipitously in a group of 20 hospitalized asthmatic patients receiving azlocillin, bronchodilators, and steroids. None of the 20 hospitalized controls receiving the antiasthma therapy without azlocillin showed any decline in their uric acid levels. The levels for the azlocillin-treated group fell from a mean of 6.4 mg/dl to mean of 2.3 mg/dl, whereas those for the control group initially were 7.0 mg/dl and fell only to a mean of 6.5 mg/dl.
Adolescent↗
Uric acid and preeclampsia.
Increased uric acid level is a key clinical feature of preeclampsia; higher levels correlate with significant maternal and fetal morbidity and mortality. The cause of hyperuricemia and its specific role in the pathogenesis of preeclampsia, however, remain unclear. Although uric acid has been shown to roughly parallel the severity of the maternal syndrome, it has not been useful in predicting the development of preeclampsia. Nevertheless, there have been recent data supporting a pathogenic role potentially in the hypertension and endothelial cell dysfunction of preeclampsia. This article reviews our current understanding of hyperuricemia in the setting of preeclampsia, and highlights the hypothesis that hyperuricemia may contribute to vascular damage in preeclampsia.
Animals↗
Comparison of the efficacy of two anti-uric acid diets in dalmatian dogs.
Commercial anti-uric acid diets for dogs may contain insufficient protein to sustain growth and lactation. In order to investigate the efficacy of an experimental purine-free diet moderately low in protein, its effect on urinary uric acid excretion was compared with that of a commercial dog food and a commercial low-protein anti-uric acid diet. The experimental diet, commercial dog food and commercial anti-uric acid diet contained 10.0, 12.8 and 5.0 g crude protein/MJ metabolizable energy, respectively. Twelve Dalmatian dogs were subjected to a 3 x 3 Latin square study. Although the plasma uric acid concentration was significantly lower when the dogs were fed either the commercial anti-uric diet (18.7 +/- 6.0 mumol/l, mean +/- SD, n = 12) or the experimental diet (19.2 +/- 8.3 mumol/l), when compared to the commercial dog food (29.2 +/- 11.1 mumol/l), no significant decrease of uric acid concentration in urine collected before the morning meal was seen. The average concentration of urinary uric acid was 60 mumol/l. There was a significant increase in the urea:creatinine ratio in urine when the dogs were fed the experimental diet compared to the commercial anti-uric acid diet, confirming that the experimental diet contained more protein. The experimental diet lowered plasma uric acid and was relatively high in protein and thus may be suitable for use in growing and lactating dogs to prevent ammonium urate urolithiasis.
Animal Feed↗
Serum uric acid is associated with microalbuminuria in prehypertension.
Serum uric acid is associated with cardiovascular disease. However, the independent role of uric acid in the development of cardiovascular disease is uncertain. This study examined the cross-sectional association of serum uric acid level with microalbuminuria among 6771 subjects without diabetes or hypertension. Blood pressure was categorized as prehypertension (systolic blood pressure, 120 to 140 mm Hg or diastolic blood pressure, 80 to 90 mm Hg) and normotension (systolic blood pressure, <120 mm Hg and diastolic blood pressure, <80 mm Hg). Microalbuminuria was found in 4.0% of normotensive subjects (n=4819) and in 7.9% of prehypertensive subjects (n=1952). Prehypertensive subjects with microalbuminuria had higher uric acid level than those with normoalbuminuria (men, 387 [68] mmol/L versus 371 [69] mmol/L; P=0.017; women 286 [56] mmol/L versus 262 [54] mmol/L; P=0.006). However, the difference in serum uric acid level according to the presence or absence of microalbuminuria was not found in the normotensive group. Multiple logistic regression models showed that, in the prehypertensive group, after adjustment for other cardiovascular risk factors, the highest uric acid quartile entailed >2 times greater risk for microalbuminuria than the lowest quartile in both men (odds ratio, 2.12; 95% CI, 1.16 to 3.87) and women (odds ratio, 3.36; 95% CI, 1.17 to 9.69). In the normotensive group, serum uric acid quartile did not show the independent association with microalbuminuria. In conclusion, serum uric acid level was strongly associated with microalbuminuria in prehypertensive subjects.
Albuminuria↗
Urate binding to serum albumin: lack of influence on renal clearance of uric acid.
Fractional excretion of uric acid (Curate/Ccreat X 100) was determined in 1 4-year-old analbuminemic child and an age-matched control. Fractional excretion of urate was 19% in the analbuminemic child and 24% in the control subject. These values are within the range reported for normal children of this age. We conclude from this study that urate binding to serum albumin is not an important determinant of the renal clearance of uric acid, and by inference there is no significant binding of urate to serum albumin in vivo.
Child, Preschool↗
Uric acid monohydrate--a new urinary calculus phase.
In our laboratory more than 100,000 urinary calculi have been analysed since 1972. Amongst this huge sample, 15 specimens originating from a total of eight patients were observed showing similar characteristics but escaping unambiguous identification with any of the substances that have been described so far in urinary concrements. Therefore, the unknown substance was submitted to a more extended analytical regimen. Structural analysis by x-ray crystallography turned out to be most successful, identifying the unknown material as uric acid monohydrate. Uric acid monohydrate crystallizes in the monocline space group P2(1)/c. Within the crystal, uric acid and water molecules form continuous layers by hydrogen bonds. This is in contrast to uric acid in its water free and its dihydrate forms, which both crystallize by forming 3-dimensional networks To the best of our knowledge , the existence of a monohydrate form of uric acid has not been reported so far. Accordingly, this is the first report on uric acid monohydrate as a urinary stone component. The frequency of only 0.015% in our survey indicates that uric acid monohydrate is rarely the main component in concrements, in contrast to uric acid and uric acid dihydrate with frequencies of 10% and 6%, respectively. The infrared spectrum of uric acid monohydrate is very similar to that of the other crystal forms of uric acid. Because of this similarity and its low frequency, uric acid monohydrate may have been overlooked as a component of urinary concrements. X-ray diffraction allows for better differentiation in routine stone analysis. All samples of uric acid monohydrate were found by solid state NMR spectroscopy to be highly contaminated by amorphous material. This material consisted of long aliphatic chains reminiscent of lipids and fatty acids, respectively. Concrements consisting of other forms of uric acid or urate lacked this amorphous component. Therefore, a role of this aliphatic material has to be taken into consideration when discussing the conditions that may favour the rare formation of concrements from uric acid monohydrate. As for as the metabolic situation of the affected patients is concerned, no common peculiarities became evident by a retrospective survey.
Aged↗
[Effects of zotepine, a psychotropic agent, on the serum uric acid level of inpatients at a psychiatric hospital].
UNLABELLED: Serum uric acid levels were examined and compared to diagnostic groups of inpatients of a mental hospital. An action lowering serum uric acid level of zotepine was further evaluated in those patients. RESULTS: (1) In patients receiving some kind of psychotropic drugs, except for zotepine, mean serum uric acid level of patients with epilepsy in both sexes was significantly lowered in comparison with that of schizophrenia. Mean serum uric acid levels of male and female patients with alcoholism and organic brain disease were higher than that of schizophrenia without any statistical significance. (2) Mean serum uric acid level of patients treated with various psychotropic drugs, except for zotepine, was higher than that of patients receiving zotepine. (3) Zotepine decreased serum uric acid level parallel with its dosage (r=0.70, p less than 0.001) with a mean reduced rate of 54.1% (p less than 0.001), when serum uric acid levels of 32 patients were examined 3 times over 3 months before and during zotepine administration, respectively. (4) Maximum reduction of serum uric acid level occurred in 3-6 days following zotepine application. Controversely, it takes about 4 weeks to recover baseline level of serum uric acid after stopping zotepine administration. (5) Zotepine had no significant effect not only on the results of creatinine clearance test, but also on BUN level. However, it significantly increased level of uric acid clearance, and rate between uric acid clearance and creatinine clearance. The rate of uric acid clearance vs creatinine clearance correlated with the dosage of zotepine given. Zotepine is thought to decrease serum uric acid level via selective blocking of tubular reabsorption of uric acid in the kidney.
Adult↗
Crystal-matrix interrelations in brushite and uric acid calculi.
Brushite and uric acid calculi were studied by means of scanning electron microscopy with the partial dissolution method and transmission electron microscopy. Brushite calculi consist of radially oriented columnar crystals which have sheet-like substructure. The organic matrix is identified chiefly at the outside of the crystals but partly included between the substructure. The concentric matrix bands are often dislocated between the neighbouring crystals. Uric acid calculi also consist of radially oriented columnar crystals, and a fine meshwork of the organic matrix is incorporated within the crystals. The concentric matrix layers of different density are angled according to the crystal lattice. These findings indicate that the organic matrix arose from a mucinous surface coat, at least in the radially striated calculi. The crystals continued to grow in this gel-state milieu, either thrusting the matrix aside or incorporating it within the crystals.
Calcium Oxalate↗
Effect of cimetidine on serum uric acid concentration.
The effect of cimetidine therapy on serum uric acid concentration was studied in four healthy men with normal renal function. Beginning four days before the 16-day study, subjects were permitted no beverages containing caffeine or alcohol and no medications and were placed on a weight-maintenance, isocaloric, purine-free 152-meq-sodium diet. On days 1-12 one cimetidine 300-mg tablet was taken four times daily; on days 13-16 no cimetidine was taken. On each study day, serum uric acid and creatinine and urine uric acid and creatinine concentrations were determined. Daily mean values for serum uric acid, total uric acid excreted, and uric acid clearance were not significantly different from baseline. No significant change occurred in creatinine excreted or creatinine clearance. Cimetidine administration to healthy men with normal renal function did not significantly affect serum uric acid concentration or renal clearance of urate.
Adult↗
Uric acid dihydrate as urinary calculus component.
The analysis of uric acid dihydrate was performed using infrared spectroscopy and X-ray diffraction. Both methods permit differentiation with regard to uric acid. Pure uric acid dihydrate was prepared according to a modified technique and the dA values (lattice distances (of A) were determined from several recordings. The extreme instability of the synthetic uric acid dihydrate is stressed, and the conversion speed is determined. During the evaluation of 7,750 analyses of urinary calculi in the course of the past 3 years, 1,126 (14.5 per cent) uric acid calculi and 283 (3.7 per cent) with a mixed portion of uric acid dihydrate were found.
Drug Storage↗
Effects of renal fuels on uptake of PAH and uric acid by separated renal tubules of the rabbit.
A rapid-filtration procedure was used to examine the effects of a wide variety of renal fuels on the uptake of p-aminohippuric acid (PAH) and uric acid (UA) by separated rabbit renal tubules. PAH and UA uptakes in 15 min over a range of substrate concentrations of 0.01-10.2 mM were determined. All tricarboxylic acid cycle intermediates and pyruvate showed biphasic stimulation of PAH and UA uptake. alpha-Ketoglutarate produced a 320 +/- 54% increase in PAH uptake and a 192 +/- 60% increase in UA uptake at 0.16 mM, the concentration at which uptake was maximal, while causing 20 +/- 3 (PAH) and 35 +/- 7% (UA) inhibition at 10.2 mM. Citrate produced a 373 +/- 19% increase in PAH uptake and a 246 +/- 41% increase in UA uptake at 0.64 mM. PAH and UA uptake were also stimulated by acetate, glucose frutose, phosphoenolypyruvate and L-glutamic acid. The data indicate a direct relationship between stimulation of PAH and uric acid transport and stimulation of renal cortical oxidative metabolism.
Aminohippuric Acids↗
Holmium:YAG lithotripsy of uric acid calculi.
PURPOSE: Holmium:YAG lithotripsy of uric acid calculi produces cyanide. We review our experience with holmium:YAG lithotripsy of uric acid calculi to determine if there is any clinical evidence of cyanide toxicity. MATERIALS AND METHODS: A retrospective analysis of all of our cases of holmium:YAG lithotripsy of uric acid calculi was done. Anesthetic and postoperative data were reviewed. RESULTS: A total of 18 patients with uric acid calculi were treated with holmium:YAG lithotripsy by ureteroscopy (5), retrograde nephroscopy (2), percutaneous nephrolithotomy (5) or cystolithotripsy (6). No patient had increased end-tidal carbon dioxide, changes in electrocardiogram or significant decrease in postoperative serum bicarbonate. An 84-year-old woman had decreased diastolic pressure of 30 mm. Hg while under general anesthesia. No cyanide related neurological, cardiac or respiratory complications were noted. CONCLUSIONS: There were no obvious cyanide related complications from holmium:YAG lithotripsy of uric acid calculi. These data suggest no significant cyanide toxicity from holmium:YAG lithotripsy of uric acid calculi in typical clinical settings. Animal studies are warranted to characterize the risk.
Adolescent↗
[Local treatment of obstructive uric acid calculi].
Dissolution of uric acid calculi could be obtained by oral or parenteral urinary alcalinization, but this method cannot apply to the case of obstructive calculi. Nineteen obstructive calculi in 18 patients were treated by in situ alcalinization through a percutaneous nephrostomy catheter (PCN). Eight patients were initially anuric, 7 of whom from an obstructed solitary kidney and 1 from a bilateral obstructive lithiasis. Fifteen calculi were located in the ureter, 3 in the uretero-pelvic junction and 1 in the pelvis. After 48 h of urinary diversion through PCN, an isotonic sodium bicarbonate solution (14 g %) was continuously infused at an average flow rate of 2.8 l/24 h, through either an unique PCN, or a 2 PCN-irrigation circuit in the 7 cases with permanently obstructive calculus. Fifteen calculi (80%) were completely dissolved after 3 to 13 days of alcalinization (average 5.8 days). One large calculus was reduced by 3/4 and further removed by percutaneous lithotripsy. Three patients underwent ureterotomy after 9 to 11 days of uneffective treatment. Local alcalinization is an effective and non invasive treatment for obstructive uric acid calculi, and is logically associated with the necessary urinary diversion.
Aged↗
Uric acid profile in patients with chronic nonspecific musculoskeletal pain.
BACKGROUND: The present study was undertaken to determine the uric acid profile in patients with unexplained chronic musculoskeletal complaints, and to establish any possible causal role for altered uric acid profile in such patients. METHOD: A comparative study of 36 patients and 36 controls of both sexes and ages between 25-60 years was carried out at Shaikh Zayed Hospital, Lahore from November 2001-May 2002. Patient included were those who had at least 4-24 weeks duration of complaints. Uric acid profile for serum uric acid, uric acid excretion, uric acid clearance and total uric acid production was done. Additional tests included renal functions test, liver function test, cardiac enzymes, haematology and serology to exclude other underlying causes of complaints. RESULTS: Mean serum uric acid levels were higher in patients as compared to controls (p = 0.05), with 9 (25%) patients showing hyperuricemia. Uric acid clearance (female patients 5.86 +/- 0.42 ml/min, female controls 8.06 +/- 0.24 ml/min) and daily uric acid excretion (female patients 412.38 +/- 28.52 mg/24 hours, female controls 487.79 +/- 18.64 mg/24 hours) in female patients was significantly lower than control females (P = 0.034 and P < 0.001 respectively). Twenty patients (55.55%, 3 males and 17 females) were classified as under excretors of uric acid, while there were no under excretors in the control group (p < 0.001). CONCLUSION: We conclude that abnormalities of uric acid profile, particularly under excretor status may be an underlying biochemical abnormality in a significant number of patients. Female patients appear more predisposed to abnormal uric acid profile such as hyperuricemia and under excretor status.
Adult↗