Effects of magnesium and calcium loading on renal excretion of electrolytes in dogs

¹ Departments of Physiology and Medicine, Cornell University Medical College, New York City

Effects of intravenous infusion of magnesium and calcium salts on excretion of electrolytes in dogs were investigated by clearance and stop-flow studies. Infusion of these salts, irrespective of the anions, caused a marked increase in the excretion of potassium and a minor change in the urinary excretion of sodium. Stop-flow studies revealed that infusion of magnesium or calcium salts increases the clearance ratios for potassium both in the proximal and the distal samples. These data could be interpreted as indicating that magnesium and calcium loading increase the excretion of potassium by interfering with its reabsorption and/or augmenting its secretion in both proximal and distal segments of the nephron. However, they can be interpreted with equal justification as indicating depression of reabsorption and/or increased secretion of potassium in either the proximal or distal segments. The stop-flow method cannot distinguish between these several possibilities.

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