Abstract
Seventy-nine young adult females collected their 24-hour urine according to the following time-schedule into separate seven parts : the urine was excreted at 9: 30, and each part of urine was collected at (1) 11: 30, (2) 13: 30, (3) 16: 00, (4) 19: 30, (5) before sleep, (6) after rising in the next morning, and (7) 9: 30, respectively. Sodium chloride, potassium and creatinine concentrations in each urine were measured. The intake of sodium chloride was calculated from the data of food consumption of each subject.
The mean daily excretion of sodium chloride corresponded to the mean figure of its intake, but the figures of the excretion and the intake did not always correspond to each other on the individual basis. Urinary sodium chloride excretion increased in the morning and decreased during sleep. About 21% of sodium chloride to daily total excretion was excreted during 7 hours sleeping period. This suggests a possibility to presume the daily intake of sodium chloride of a group from the excretion in the urine during sleep. Potassium excretion also deminished during sleep. Three peaks of Na/K ratio were observed in a day, corresponding after respective meals. Creatinine excretion decreased slightly during sleep. The decrement was so small that it is possible to estimate the daily sodium chloride excretion from the measurement of NaCl/creatinine ratio of the urine partially collected, especially that during sleep.
