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In order to further characterize the basic pattern of electrolyte and nitrogen metabolism of the Korean, 24-hour urines were collected from 1,260 male subjects who were randomly selected from three different geographical areas (city, rural and island) in age from 6 to 25. For the city subjects, studies were conducted in both summer and winter for a seasonal comparison, while the other subjects were studied in the autumn only. Of these subjects, blood samples were also obtained from 225. In all groups, the serum composition of electrolytes including proteins was within normal range. The daily urine output which increased as a function of age was somewhat greater in summer than in winter. The daily urine output per unit surface is decreased inversely according to age. On the other hand, the urine osmolality which increased with age was higher in winter than in summer. The daily salt excretion which was greater in summer than in winter increased according to age, although the daily salt excretion per unit surface area was constant regardless of age. The daily potassium excretion was such that the urinary K/Na ratio decreased according to age while it was higher in winter than in summer. Likewise, the daily nitrogen excretion was much greater in winter than in summer while it increased with age. However, the daily nitrogen excretion per unit surface area decreased in older subjects age. In contrast to these seasonal differences in respect to certain electrolytes and nitrogen excretion, there was no distinct geographic difference in these variables. Moreover, many of the above variables changed according to age, but tended to stabilize at the age of approximately 15 years. A comparison of the present data with others indicates that the daily urine output and the daily salt excretion are greater while the urine osmolality, the daily nitrogen excretion and the urinary K/Na ratio are lower in the Korean than in the occidental. Moreover, these results strongly suggest that Korean people acquired a habit of ingesting low-protein and high-salt diets at the age of 6 years or perhaps before.
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