ABSTRACT
It is known that the reabsorption of filtered HCO<SUB>3</SUB><SUP>-</SUP>depends on the tubular flowrate in the proximal uniferous tubule. In animal experiments, studies have demonstratedthat, when diuresis was induced, the pH of the collecting duct urine decreased, resulting from the decrease in HCO<SUB>3</SUB><SUP>-</SUP>concentration with no change in the pCO<SUB>2</SUB> level.The present study was designed to examine changes in urine acidification in humansunder a water diuretic state. Urine pH, pCO<SUB>2</SUB> levels, and HCO<SUB>3</SUB><SUP>-</SUP>concentration weremeasured before and after the drinking of water. In 120 minutes after hydration, theurine pH level fell about 0.5 pH unit from that before the intake of water. The urine HCO<SUB>3</SUB><SUP>-</SUP>concentration coincidentally decreased significantly. However, pCO<SUB>2</SUB> values remainedunchanged. These results indicated that also in humans, water diuresis promotesurine acidification, resulting from a decrease in HCO<SUB>3</SUB><SUP>-</SUP>concentration with nochange in the pCO<SUB>2</SUB> level, which may contribute to the prevention of the loss of plasmaHCO<SUB>3</SUB><SUP>-</SUP>into the urine when the urine flow rate increases.
ABSTRACT
This study was designed to examine the relationship between exercise diuresis and running load, following seven types of running events by five male athletes, aged 19 to 25 years. None had a history of renal disease.<BR>Informed written consent was obtained from all subjects prior to the study.<BR>1. Compared to the resting levels, significant increases in the urinary volume were observed thirty minutes after performing a 400-meter dash, but not after the other exercises.<BR>2. The changes in creatinine concentration (30 min after exercise/after warm-up) were inversely proportional to the changes in urinary volume, indicating that exercise diuresis depends on the depressed reabsorption of water in the renal tubules.<BR>3. The absence of diuresis after 60 and 100-meter sprints, indicates that the phosphagen system is mainly employed for energy supply.<BR>4. The urinary volumes after 200, 300 and 400-meter dashs highly correlated with the changes in the excretion rate of pyruvate. This suggests that exercise diuresis is related to the lactic system in energy metabolism.<BR>5. The decreased excretion rate of creatinine after 800 and 1, 500-meter runs indicates that GFR is reduced by these exercises. Furthermore, the lactic energy system caused the diuretic effect. Thus, even though secretion of antidiuretic hormones is increased following exercise, their effectiveness is reduced by lactic oxygen deficit.