Effect of parathyroidectomy on content and availability of skeletal sodium in the rat

¹ Departments of Medicine and of Biochemistry, Harvard Medical School, Boston, Massachusetts

The effect of parathyroidectomy on the composition of plasma and bone has been examined in rats with and without sodium depletion. Parathyroidectomy caused a marked fall in calcium and a slight decrease in chloride in the plasma and a 7.9% increase in bone mineral sodium concentration. Sodium depletion by intraperitoneal dialysis of normal animals lowered bone mineral sodium 4% while plasma sodium and pH remained at almost normal levels. In contrast, sodium depletion following parathyroidectomy failed to lower bone sodium significantly but produced a significant acidosis and a slight decrease in plasma sodium. These findings suggest that the ability of bone to release sodium ions to protect extracellular fluid pH in acute sodium depletion is dependent on the presence of the parathyroid glands. Possible mechanisms by which parathyroid activity might influence bone sodium metabolism by changes in bone cell metabolism, changes in the Na:Ca ratio of extracellular fluid, or actual bone destruction are discussed.