ABSTRACT

Abnormalities of purine metabolism are often found in clinical practice, notably hyperuricaemia and gout. Urate is the end product of purine metabolism in humans. Purines synthesized in the body, those derived from the diet and those liberated by endogenous catabolism of nucleic acids may be oxidized to urate or reused for nucleic acid synthesis. Urate is filtered through the glomeruli and most is reabsorbed in the proximal tubules. Renal secretion may be enhanced by uricosuric drugs, which block tubular urate reabsorption. Urate is poorly soluble in plasma. At plasma pH, most urate is ionized at position 8 of the purine ring. In acute attacks of gouty arthritis, local factors are more important than the plasma urate concentration, which is usually normal during the attack. Plasma urate concentrations are low in children and rise in both sexes at puberty, more so in males than in females; concentrations are highe.