External factors affecting diurnal variation in electrolyte excretion with particular reference to calcium and magnesium

Abstract

1. 1. The effect of exercise, urine flow and food intake on the renal excretion of calcium, magnesium, water, sodium, potassium, phosphate and creatinine was observed in normal adults. 2. 2. In fasting subjects the rate of calcium and magnesium excretion was greater during the night than daring the day, irrespective of whether the subjects were at rest or active during the day. 3. 3. When the subjects were receiving normal meals, the excretion rate of calcium and magnesium was usually greater during the day than during the night. 4. 4. A rapid rise in the excretion of calcium and magnesium occurred after a meal, the average rate of excretion increasing two to four times in the first 3 h and then decreasing during the next 12–15 h- No significant effect on the excretion of sodium, potassium, creatinine or phosphate was observed. 5. 5. The excretion of calcium and magnesium was reduced during moderate exercise bat the excretion of sodium, potassium, creatinine, and inorganic phosphate was unaffected. 6. 6. No correlation was found between urine flow and the excretion of calcium or magnesium during water diuresis but there was a significant correlation between urine flow and the excretion of sodium and potassium.