Renal handling, of uric acid

Renal handling of uric acid. Uric acid may be actively reabsorbed from the ultrafiltrate following its glomerular filtration or it may be secreted from the blood across the basolateral membrane into the proximal tubular cell. Both passive and active transport mechanisms are involved in the handling of urate. Uricosuric drugs at appropriate doses interfere with these processes. 

Fanelli GM (1976) Drugs affecting the renal handling of uric acid. In Martinez-Maldonado M (ed) Methods in Pharmacology. Vol 4A Renal Pharmacology. Chapter 9. Plenum Press, New York, London, pp 269-292 Friedman M, Byers SO (1948) Observations concerning the causes of the excess excretion of uric acid in the Dalmatian dog. J Biol Chem 175 727-735... 

Renal handling of uric acid is complex and involves four sequential steps (1) glomerular filtration of virtually aU the uric acid in capillary plasma entering the glomerulus (2) reabsorption in the proximal convoluted tubule of about... 

Sorensen, L.B., Levinson, D.J. Evidence for four compartments in the renal handling of uric acid in man. In Amino Acid Transport and Uric Acid Transport. (Eds. S. Silbernagl, F. Lang, R. Gre-ger) Georg Thieme Publishers, 1976, pp 243-247. 

RENAL HANDLING OF URIC ACID IN NORMAL SUBJECTS ITS BEHAVIOUR WITH RESPECT TO DIFFERENT FILTERED LOADS... 

The investigation was conducted with the voluntary cooperation of 10 normal males (mean age, 33 years) who were placed on an essentially purine-free diet during the study. Renal handling of uric acid was examined by means of the pyrazinamide (PZA) and probenecid (PB) tests, performed in three uricemia states normouricemia 3.6 to 6.4 mg/dl), allopurinol-induced hypouricemia (under 3.5 mg/dl), and hyperuricemia after oral administration of RNA monosodium salt (over 6.5 mg/dl). 

Table 1 shows daily uric acid excretion, serum urate levels, and the different tubular phases of the renal handling of uric acid under the three uricemia states. Presecretory reabsorption of filtered uric acid was always above 99%. Tubular secretion of uric acid expressed as the percentage of filtered urate, was significantly higher in hyperuricemia with respect to the hypouricemia state. Tubular reabsorption of secreted uric acid was similar in normouri-cemia and hypouricemia, but in the sate of hyperuricemia a significant diminution of uric acid postsecretory reabsorption could be evidenced. 

RENAL HANDLING OF URIC ACID IN NORMAL SUBJECTS... 

D. J. Levinson, and L. B. Sorensen, Renal handling of uric acid in normal and gouty subjects evidence for a 4-component system, Ann. Rheum. Dis. 39 173 (1980). 

Fifty patients (22 males and 28 females mean age 46 years) were consecutively referred to our Metabolic Unit for the evaluation of recurrent nephrolithiasis. Diagnosis was made on the basis of spontaneous emission or chirurgical extraction of two or more calculi with an interval superior to one year. In every patient we performed a metabolic study and the results were compared with those obtained in 20 controls (10 males and 10 females mean age 33 years) Hyperuricosuria was defined as daily uric acid excretion above 800 mg for men and 750 mg for woman, while on a purine-free diet. Renal handling of uric acid ms evaluated by means of pyrazinamide (PZA) and probenecid (PB) tests. ... 

Data concerning renal handling of uric acid appears in Table 2. The administration of an essentially purine-free diet normalized uricosuria in 4 patients. PZA and PB tests were within normal limits in these patients, suggesting that hyperuricosuria could be related to purine overingestion. Five patients remained hyperuricosuric even under an essentially purine-free diet, and 2 were hypo-... 

Dietary habits and tubular transport defects of urate explain the excessive uric acid excretion of patients with RCN. An alteration of the renal handling of uric acid may be suspected when hyperuricosuria concurs with hypouricemia normal serum uric acid does not exclude a tubular transport defect of urate. 

Renal handling of uric acid was examined in 30 patients with primary gout (mean age, 44 years), and in 10 normal controls (mean age, 33 years). A normal GFR, as assessed by means of endogenous creatinine clearance, was a pre-requisite for being included in the... 

Twenty-four hour urinary urate excretion, when expressed in mg/day or mg/Kg, is valuable to ascertain whether a patient underexcretes uric acid or not, but in a particular case may not differentiate patients with normal renal handling of uric acid from those with reduced tubular secretion of urate. 

The clinical manifestations of gout, i.e. articular and renal disease, are intimately connected with hyperuricemia and/or particularities of renal handling of uric acid. It is well established that normalization of plasma uric levels will cure the joint disease. The diminution of renal uric acid excretion by administration of allopurinol will cure nephrolithiasis in its uncomplicated forms. One may presume that the other manifestations of the gouty kidney (i.e. parenchymal renal disease, hypertension and azotemia) will also be influenced by a therapy reducing urinary uric acid however no reliable reports exist as yet on this point. 

Renal handling of uric acid was studied in detail in 11 male and 5 female adults, mean age 25, with sickle cell anemia (Table 1). Mean serum uric acid was 7.0 0.7 mg%. Eight patients were hyperuricemic and 8 were normouricemic. All but 1 of the 16... 

Fig. 2. Effect of ethambutol on serum urate concentration and renal handling of uric acid.

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