Abstract
Changes in urinary excretion of hydrogen peroxide (H2O2) by exercise was determined in eight healthy subjects. Urinary H2O2 was determined according to Varma's method based on the decarboxylation of 1-14C-alpha-ketoglutaric acid by H2O2. The liberated 14CO2 was counted by a liquid scintillation counter. Urine sample was diluted to 1:50 with Tyrode buffer, and the amount of water load was 50 ?? 300 ml/h with an average of 141.7 ml/h. Exercise was performed by bicycle ergometer for 30 minutes at the intensity of 80% and 40% of maximum heart rate predicted by age. When they were at rest with only water load, urine volume significantly increased during the first 2 ?? 3 h, whereas it increased slightly by exercise at the intensity of 80%. The urinary excretion rate of H2O2 increased slightly in the mode at the rest, whereas it decreased immediately after exercise at the intensity of 80%, followed by an increase 3 hr after exercise, and the subsequent decrease thereafter. At the exercise intensity of 80%, urinary excretion rate of H2O2 was significantly lower than that in rest mode. The results obtained in this study indicated that measurements of the urinary H2O2 excretion rate was demonstrated quantitative, suggesting that the urinary excretion rate of H2O2 in urine may be affected by water diuresis and sodium reabsorption at tubules.
