Urate deposition disease. How is it regulated and how can it be modified?

Lessons from Carl M. Pearson 1919 - 1981

Carl M. Pearson was an energetic and exceptional physician-scholar-leader who founded, established, and broadened the Divisions of Rheumatology at University of California in Los Angeles (UCLA) beginning in 1956. His studies to induce myositis by injecting muscle saturated with the heat-killed tubercle bacillus, an emulsifier, and mineral oil (Freund's adjuvant) enabled his report that polyarthritis occurred with Freund's adjuvant alone in certain strains of rat and mice. This model of adjuvant arthritis allowed the next generation of studies to assess therapies for autoimmune diseases.

Implications of disorders of purine metabolism for the kidney and the urinary tract

The spectrum of kidney and urinary tract disorders related to purines comprises acute hyperuricosuric nephropathy, chronic urate nephropathy and urolithiasis. Two factors in the development of acute hyperuricosuric nephropathy are increased uric acid concentration and low pH in the tubular fluid. Chronic urate nephropathy still possess several problems: incidence (although this seems to be decreasing, presumably owing to effective prevention), the source of interstitial urate, the cause of the interstitial deposition of urate, and the role of urate deposits in the pathogenesis of the interstitial nephropathy. The relation of the experimental nephropathy to the pathogenesis of chronic urate nephropathy in the human is not yet clear but a model is proposed according to which interstitial urate derives from two sources: hyperuricaemic plasma and hyperuricosuric tubular fluid. Urolithiasis related to purines leads to uric acid-urate stones, xanthine stones, 2,8-dihydroxyadenine stones, iatrogenic xanthine and oxipurinol stones, and possibly calcium stones. Pathogenetic factors in uric acid lithiasis are hyperuricosuria (whether due to an inborn enzyme abnormality or of unknown aetiology) and low urinary pH; oliguria is a contributory factor. There remain several open questions about uric acid lithiasis: incidence, the shift of its location from lower to upper urinary tract, the interplay of pathogenetic factors, and the role of compounds which inhibit crystallization.

Serum 17-beta-estradiol and testosterone levels in asymptomatic hyperuricaemic men

Low levels of oestrogen, FSH and LH in serum have been reported in patients with gout. The mechanism by which sex hormones affect the development of gout is unknown, but some investigators believe that it is related to the influence of oestrogens on serum uric acid levels. We studied the relationship between serum uric acid and 17 beta oestradiol (ES) levels in asymptomatic hyperuricaemic (ASH) men in order to test the hypothesis that low ES levels are associated with hyperuricaemia. Thirty-eight men with asymptomatic hyperuricaemia (ASH) were selected from a population of healthy individuals undergoing periodical multiphasic health examinations. After adjusting for the differences in albumin levels between the two groups, no significant difference in serum ES level was found. The serum testosterone levels were similar in both groups. These findings suggest that there is no difference in the sex hormone profiles between asymptomatic hyperuricaemic and normouricaemic men.

Acute uric acid nephropathy

Uric acid, as the end-product of purine metabolism in humans, presents a clinical problem because of its relative insolubility, particularly in the acid environment of the distal nephron of the kidney. As a result, states of enhanced purine catabolism increase the urate load on the kidney, leading to intrarenal precipitation. Major causes of increased purine metabolism are malignancies with rapid cell turnover, such as leukemias and lymphomas, and the added acceleration of cell lysis that occurs with chemotherapy and radiation. Serum urate levels rise rapidly, and acute renal failure occurs as a consequence of tubular deposition of urate and uric acid. The keys to the diagnosis of acute uric acid nephropathy are the appropriate clinical setting of increased cell lysis, oliguria, marked hyperuricemia, and hyperuricosuria. A urinary uric acid-to-creatinine ratio greater than 1 helps to distinguish acute uric acid nephropathy from other catabolic forms of acute renal failure in which serum urate is elevated. Preventive treatment involves pharmacologic xanthine oxidase inhibition with allopurinol and alkaline diuresis. Occasionally, acute renal failure occurs despite allopurinol because of the tubular precipitation of the precursor metabolites, such as xanthine, which accumulate with xanthine oxidase inhibition. Dialysis therapy may be required both to correct azotemia and to reduce the body burden of urate. Hemodialysis is preferred because it can achieve greater clearance than other dialysis modes.

Renal disease from excess uric acid

Excess uric acid or urate deposition is a common element in three different forms of renal disease: acute uric acid nephropathy, chronic urate nephropathy, and uric acid nephrolithiasis. Clinical features vary with each form. Therapy is directed at decreasing production of uric acid, increasing its solubility, or both. When possible, preventive measures are taken.

Oncologic emergencies I. Metabolic and space-occupying consequences of cancer and cancer treatment

Proper management of the consequences of cancer and cancer treatment is necessary to give affected children the increased chances of survival that recent therapeutic advances offer them. This article discusses the pathophysiology, diagnosis, and management of those metabolic and space-occupying consequences that are likely to face the primary care physician.

The binding of urate to plasma proteins determined by four different techniques

Venous occlusion in healthy individuals showed no binding of urate under conditions when the expected increased levels of known bound species was demonstrated. Ultrafiltration of serum from 10 healthy controls and five gouty individuals also showed the absence of binding in all cases, as did electrophoretic and chromatographic studies.

Uric acid effects on in vitro models of rheumatoid inflammatory and autoimmune processes

A neutrophil monolayer system was used to study the effects of uric acid on neutrophil-aggregate interactions important in rheumatoid inflammation. No effect on immunoglobulin G aggregate phagocytosis was seen, but hyperuricaemic levels of uric acid were associated with an enhancement of phagocytosis-induced release of the azurophilic granular enzyme beta-glucuronidase. A trinitrophenyl-coupled mononuclear leucocyte rheumatoid factor plaque-forming assay was utilised to study uric acid effects on polyclonal activation of immunocompetent cells. Low levels of uric acid enhanced and high levels suppressed this system. Hyperuricaemia may enhance some aspects of rheumatoid inflammation, while uric acid may modulate an important component of rheumatoid autoimmunity.

Cancer and the kidney: complications of neoplasms

Various renal complications occur during the course of neoplastic disease. The therapeutic and prognostic implications differ according to the reversibility of both the underlying malignancy and the superimposed complications in the kidney. Since the mechanisms of renal failure vary significantly in patients with different types of malignancy, it is essential to avoid generalizations about etiologic factors or likely outcomes of the disease processes. The pathophysiologic abnormalities should be determined in each patient, and the reversibility of both the neoplastic and problems assessed before therapeutic decisions are made. This often requires a team effort by the internist, oncologist, nephrologist, urologist and, most importantly, the patient.

Plasma and synovial fluid as solvents for monosodium urate

In-vitro differences in monosodium urate (MSU) crystal dissolution in paired plasma and synovial fluid samples from patients with various arthritides were studied. Plasma was a significantly better solvent for MSU than synovial fluid (overall difference 6.3 mg/dl (0.37 mmol/l); significant at P less than 0.001). Attempts to correlate the solubility differentials with the principal compositional differences between the 2 fluids were only partially successful. (1) A tendency towards higher MSU solubility at higher protein levels was observed, but it was too slight to reach statistical significance. (2) Hyaluronidase treatment of synovial fluid significantly enhanced its ability to dissolve MSU (overall difference 2.2 mg/dl (0.13 mmol/l); significant at P less than 0.01) but not sufficiently to explain wholly the plasma-synovial fluid differential.

Acute tumor lysis syndrome. A review of 37 patients with Burkitt's lymphoma

Renal and metabolic complications of tumor lysis during 46 episodes of remission induction chemotherapy were reviewed in 37 patients with American Burkitt's lymphoma. Azotemia occurred in 14 patients, preceding chemotherapy in eight. All of these patients had abdominal tumors. Pretreatment azotemia was associated with elevated lactic dehydrogenase (LDH) and uric acid levels, and sometimes extrinsic ureteral obstruction by tumor. Two patients required dialysis for uric acid nephropathy before chemotherapy was initiated. Following chemotherapy, major complications of tumor lysis (hyperuricemia, hyperkalemia and hyperphosphatemia) were associated with very large tumors, high LDH levels and inadequate urinary output. In patients undergoing diuresis and receiving allopurinol, hyperkalemia or hyperuricemia developed infrequently unless concomitant renal failure ensued. Hyperphosphatemia, which occurred only after chemotherapy, developed in 10 of 32 (31 per cent) nonazotemic and in all azotemic patients. Hemodialysis was required in three post-treatment patients for control of azotemia, hyperuricemia, hyperphosphatemia and/or hyperkalemia. Because of the potential for renal failure caused by precipitation of phosphate, severe hyperphosphatemia is an additional criterion for dialysis in patients with acute tumor lysis syndrome.

High steady-state levels of uric acid produced in rats by dietary training and potassium oxonate

To reduce the inherent variability in serum uric acid levels of animals allowed ad libitum exposure to food containing potassium oxonate and uric acid, male Sprague-Dawley rats were trained to eat their daily food allotment in a 1.25-hr period each morning. After training the rats were fed a food mixture containing 5% potassium oxonate and 2% uric acid (w/w each). Serum blood levels of uric acid reached a steady state within 2 hr; these levels were maintained for an additional 4 hr. It is believed that the stomach emptying rate is a zero-order process under these experimental conditions.

A micropuncture study of the early phase of acute urate nephropathy

The early pathophysiological changes in acute urate nephropathy were investigated in a rat model using micropuncture, clearance, and morphologic methods. Plasma urate was increased from 1.2 +/- 0.6 to 20.1 +/- 3.1 mg/100 ml (P less than 0.001). Urinary urate rose from 24.3 +/- 5.1 to 142.2 +/- 21.0 mg/100 ml (P less than 0.001). Renal plasma flow and glomerular filtration rate fell to 17 and 14% of control values, respectively, and urine flow rate decreased from 11.3 +/- 4.8 to 4.2 +/- 2.2 mul/min (all P less than 0.005) Superficial nephron filtration rate fell less than that of the whole kidney (70 vs. 86%). Both proximal and distal tubular pressures were increased from 10.6 to 26.1 mm Hg and from 7.2 to 24.7 mm Hg, respectively (P less than 0.005). Efferent arteriolar and peritubular capillary pressures were increased twofold. Vascular resistance beyond the peritubular capillaries increased from 4.8 X 10(9) to 21.6 X 10(9) dynes s/cm5. Extensive deposits of uric acid and urate were found in the tubular system and vasa recti from the corticomedullary junction to the tip of the papilla. It is concluded from these experiments that not only tubular obstruction in the collecting ducts, but also obstruction of the distal renal vasculature, are the primary early pathogenetic events in acute urate nephropathy.

Current concepts of the mechanism of acute inflammation in gouty arthritis

The acute gouty attack develops after free crystalline monosodium urate crystals appear in the joint cavity (1). Recent developments in the investigation of urate crystal-induced inflammation have led to a better understanding of the pathogenesis of acute gouty arthritis. The purpose of this review is to summarize present concepts concerning the mechanism of the acute gouty attack.