INFLUENCE OF THE RENAL EXCRETION OF SODIUM CHLORIDE UPON THE RENAL EXCRETION OF MAGNESIUM AND OTHER IONS BY HUMAN SUBJECTS*

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Abstract
Alterations in the rate of urinary excretion of magnesium in human subjects receiving a constant diet are consistently produced by imposing conditions resulting in pronounced changes in the rate of urinary excretion of sodium and chloride. Diminished urinary salt excretion, whether occurring as a result of reduced salt intake or of increased adreno-cortical activity, is accompanied by diminished urinary magnesium excretion, and augmented urinary salt excretion produced by withdrawal of exogenous or endogenous adrenocortical hormones is accompanied by increased urinary magnesium excretion. Prevention of the usual effect of diminished adrenocortical activity upon urinary sodium chloride excretion also prevents its effect upon urinary magnesium excretion. Moreover, the effect of salt restriction upon urinary magnesium is equally great in normal subjects or in severely adrenal-deficient patients. Therefore adrenocortical hormones affect urinary magnesium excretion as a consequence of affecting urinary sodium chloride excretion, and no adrenocortical hormone mediates the changes produced in urinary magnesium excretion by varying the dietary salt intake. Other data suggest but do not prove that the observed changes in urinary magnesium excretion reflect primary alterations of renal magnesium clearance resulting from changes in net renal tubular reabsorption of filtered magnesium. It is not possible at present to define the relative importance of sodium versus chloride ions in relation to the observed effects of variation in the rate of urinary sodium chloride excretion. Limited but significant data show that when urinary sodium chloride excretion is altered, the rate of urinary excretion of calcium parallels that of sodium, chloride and magnesium.