Mechanism of exercise-induced hyperuricemia

This study was designed to make clear why increases and decreases in serum uric acid levels after vigorous exercise were delayed. Eight healthy male subjects who were given allopurinol before exercise participated in this study. We performed exhaustive exercise test on bicycle ergometer, and investigated the changes in purine metabolites levels in blood and urine. Results were summarized as follow; 1) Serum uric acid concentrations did not change significantly. Urinary excretions of uric acid decreased from 30 minutes to 1 hour after exercise, and recovered thereafter. 2) Plasma oxypurines concentrations exhibited the maximum level at 1 hour after exercise, and maintained the higher levels until 7 hours after exercise. Urinary oxypurines excretions exhibited the maximum level at 1 hour after exercise, and maintained the higher levels until 24 hours after exercise. 3) Plasma inosine concentrations increased only in one subject. Plasma hypoxanthine concentrations increased significantly in all subjects. Plasma xanthine concentrations did not change. 4) Blood ammonia concentrations exhibited the maximum level at 5 minutes after exercise, and returned to basal levels at 2 hours after exercise. These observations suggest that the delays of increases and decreases in serum uric acid levels are due to that the prolonged release of hypoxanthine from skeletal muscle lead to the prolonged production of uric acid in liver.