Renal Excretion of Calcium and Phosphate in the Mouse as Influenced by Parathyroids. ∗

Summary

Changes in renal excretion rates of calcium and phosphate, as affected by parathyroidectomy and parathyroid extract administration, were studied in mice. Parathyroidectomy temporarily increased urinary calcium values to 3 times control values, while decreasing phosphate excretion to 1/3 normal values. Urinary excretion of both ions returned to within normal range by 14 hours after start of experiment. Parathyroid extract administration produced opposite changes of about the same magnitude. Urinary calcium values decreased while those for phosphate rose. These changes were also temporary. Results are interpreted as due to changes in renal tubular reabsorption rates for the 2 ions, causing altered excretion rates until plasma levels adjust to the new renal thresholds. Particular emphasis is placed on changes in renal calcium excretion. These studies demonstrate parathyroid influences on handling of calcium by the kidney for a fourth mammalian species, suggesting the importance of this little considered aspect of the action of parathyroid hormone in overall parathyroid physiology.