We investigated the effect of the difference of exercise intensity on the changes in ammonia and oxypurines (hypoxanthine·xanthine) . The subjects were 7 male university students who belonged to the Judo club. By using a bicycle ergometer with the same total work load (kpm), they performed following exercise : light exercise (27.1±0.8% HRmax), moderate exercise (72.6±2.5% HRmax) and exhaustive exercise. After light exercise, blood ammonia, serum oxypurines and urinary oxypurines excretion did not increase. Urinary uric acid excertion increased significantly, but serum uric acid decreased slightly. After moderate exercise, the significant increase was observed with blood ammonia (+ 35.3±5.9μmol/l) . Urinary oxypurines excretion also increased significantly, while serum oxypurines did not change. Also, serum uric acid rose slightly. After exhaustive exercise, the significant increase was observed with blood ammonia, serum oxypurines and serum uric acid. Each peak level and appearance time were +67.2±15.1μmol/l after 3 min, +31.4±7.6μmol/l after 30 min, 155.7±39.9μmol/l after 1 hr of exercise, respectively. These results suggest that AMP deamination occur during moderate intensity, while remarkable production of oxypurines which lead the increase of serum uric acid occur in higher exercise intensity.

In order to elucidate effects of the exercise intensity on purine catabolism, we performed exhausitve exercise (Exh-ex), 80% VO₂max exercise (80%-ex) and 70% VO₂max exercise (70%-ex) test by a bicycle ergometer, and estimated the purine catabolism by the changes in blood ammonia, plasma oxypurines and urinary oxypurines in five healthy male subjects who were given allopurinol. The results were summarized as follows;
1) Plasma oxypurines concentrations (POP) increased gradually after exercise with each intensity. The order of their maximal levels and of cumulative areas under the curves of POP were exh-ex>80%-ex>70%-ex>control, respectively, and that of urinary excretions of oxypurines was exh-ex>80%-ex>70%-ex≥control.
2) Blood ammonia concentrations (BNH₃) increased sharply after exercise with each intensity. The order of their maximal levels was 80%-ex = exh-ex>70%-ex>control, and that of cumulative areas under the curves of BNH₃ was 80%-ex>exh-ex>70%-ex>control.
3) Blood lactate concentrations (BLA) increased sharply after exercise with each intensity. The order of their maximal levels and of cumulative areas under the curves of BLA were exh-ex =80%-ex>70%-ex>control, respectively.
These results suggest that the purine catabolism leading to uric acid production is activated by the physical exercise in the order of increasing intensities. The discrepancy between the increase in ammonia and those in oxypurines suggests that the increased purine catabolic pathway was mediated not only by AMP deamination but also by other factors.