Some Effects of Magnesium Loading upon Renal Excretion of Magnesium and Certain Other Electrolytes1

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Abstract
Nonpregnant and pregnant normal, hypertensive and preeclamptic women were injected with magnesium acetate or sulfate, given in a variety of ways. The renal clearances of Mg++ increased as a roughly linear function of the serum Mg++ concentration and the attendant anion-acetate or sulfate-had no discernible effect, Ultrafiltrable serum Mg++ was derived from a nomogram and "corrected" Mg++ clearances calculated. The ratio of such clearances to the inulin clearance approached 1 at the highest levels of serum Mg++ studied. Increments in the filtered load of Mg++, over "basal" levels, were excreted almost completely. The injection of Mg++ salts was followed by augmented urinary excretion of Ca++; the increase in Ca++ excretion bore a direct relationship to the serum Mg++ concentration. Stimulation of Na+ and Cl- excretions was observed as long as the serum Mg++ concentration was rising. When the serum Mg++ became constant, or fell, the excretions of Na+ and Cl- dropped back toward, to, or below control levels. The effect of Mg++ upon K+ excretion was variable.