Determination of urinary excretions of aldosterone and sodium by short term collections of urine in healthy men.

The study was designed to evaluate the usefulness of urinary aldosterone and sodium excretions (AER and UNaV) determined for 4- and 12-hour period in providing an accurate reflection of daily AER and UNaV. Nine healthy young male volunteers were fed diets contained varying amount of sodium for a period of 4 days; 34 mEq/day as low-salt, 450 mEq/day as high-salt and 194 mEq/day as control diet. Urine collection was made every 4 hours starting at 8:00 a.m. for 24 hours on the last day of each period. The values for 12- and 24-hour urine were obtained by the sum of those for 4-hour collections. The values for both AER and UNaV for every 4-hour showed remarkable circadian rhythms in any of 3 different dietary sodium intakes. The correlation between any 4-hour value for AER or UNaV for and 24-hour value was highly significant (p < 0.001). The values for AER or UNaV, expressed per gram creatinine excretion, also revealed highly significant correlation between any 4- or 12-hour and 24-hour period (p < 0.001). Highly significant correlations were also observed between thesupineplasma aldosterone concentration and the preceding 12-hour (p < 0.001) or 24-hour AER (p < 0.001). It can be concluded that AER and VNaV measured in 4-hour or 12-hour period are a valid reflection of AER and UNaV for 23 hours.