Renal excretion of calcium and magnesium during correction of metabolic acidosis by bicarbonate infusion in the dog

Bicarbonate administration has been reported to decrease the fractional excretion of calcium but its effect on absolute calcium and magnesium excretion has not been examined. The present investigation was performed to characterize the site and action of bicarbonate on the renal excretion of calcium and magnesium. Mongrel dogs were made chronically acidotic by feeding NH₄Cl and thyroparathyroidectomized before the acute infusion of either 0.7 M NaCl or 0.7 M NaHCO₃. Sodium cloride infusion had no effect on calcium or magnesium excretion. In contrast, bicarbonate infusion decreased the absolute and fractional excretion and increased the absorption of both cations despite increases in their filtered loads, and in the absence of parathyroid hormone. These results suggest that bicarbonate exerts a direct renal effect to decrease calcium and magnesium excretion.