Renal Handling of Uric Acid in Normal Subjects by Means of the Pyrazinamide and Probenecid Tests

Abstract

Pyrazinamide and probenecid tests were used to study the renal mechanisms for urate excretion in 10 normal subjects in the state of low serum uric acid levels (below 3.5 mg/dl), normal serum urate concentrations (between 3.6 and 6.4 mg/dl) and high serum uric acid levels (above 6.5 mg/dl). Presecretory reabsorption of urate was above 99% in all three conditions of uricemia, indicating that filtered urate is nearly completely reabsorbed in the proximal tubule regardless of serum uric acid concentrations. Urate secretion was significantly higher and postsecretory reabsorption was significantly lower when serum uric acid was raised than when serum urate levels were normal or low. The findings indicate that both urate secretion and postsecretory reabsorption play a role in urate homeostasis in states of hyperuricemia.

Uric Acid Excretion and Dopamine-Induced Glomerular Filtration Response in Patients with IgA Glomerulonephritis

“…Urinary uric acid excretion is based on the multicompartmental model of renal handling, assuming pre- and postsecretory reabsorption [23]. It was shown that both pre- and postsecretory reabsorption values have a tendency to decrease while the renal function declines [24]. The IgA patients showed a lower filtration rate than the controls; therefore, we presume that the higher fractional uric acid excretion was due to the decreased pre- and postsecretory reabsorption.…”

“…It is very likely that the decreased pre- and postsecretory reabsorption could be the consequence of disturbances of the peritubular vessel function. To prove this hypothesis, it would be desirable to employ pharmacological tests with pyrazinamide and probenecid [24]. …”

Hyperurícemia and Increase in Postsecretory Reabsorption of Uric Acid

“…It has been stated that there would be a normal tubular management of uric acid in gout and, in some cases, a decrease in tubular secretion caused by hyperuricemia [7]. In both of our patients, another possible renal cause of hyperuricemia can be suspected: an increase in postsecretory reabsorption, which should be considered in gouty patients.…”

“…The different components of uric acid tubular ma nagement can be determined by the pyrazinamide and sulfinpyrazone tests, and the normal adult values have already been established [5], Hyperuricemia has been reported to be due to differ ent etiologies which include both abnormalities in the purine metabolism and a familiar type of tubulointersti tial nephropathy, which is commonly associated with gout.…”

“…Both patients, following a normal diet and without any medication, were submitted to the pyrazinamide and sulfinpyrazone test, according to what has been previ ously described in the literature [6]. The results are shown in table II, and compared to those reported for adults [5].…”