The Effect of Experimental Hyperphosphatemia on Calcium and Phosphorus Excretion.

Abstract

Abnormal levels of serum phosphorus are found in association with various metabolic disturbances, such as renal insufficiency, hyper and hypo-parathyroidism, rickets and osteomalacia. In this study, we have attempted to determine the effect of experimental hyperphosphatemia upon some of the other constituents of the serum, and upon the urinary constituents. The work was planned to supply values which could be used as standards of comparison for future studies, using animals that will be subjected to various procedures which might be expected to alter their mineral metabolism. Sodium glycerophosphate injections were used to raise the serum phosphate level. The glycerophosphate was chosen because it was thought that it would be tolerated in larger amounts than the inorganic salt, and because of the growing opinion that phosphate esters may play an important rôle in the metabolism of calcium and phosphorus. Dogs were given intravenous injections of 50% solution of sodium glycerophosphate, in amounts equivalent to 0.1 gm., 0.25 gm., 0.5 gm., and 1.0 gm. per kilo of body weight. The preparation contained 11% of phosphorus, and gave no test for inorganic phosphate. In control experiments on the same animals, phosphate was given as the sodium salt, pH 7.4, in amount equivalent to 0.5 gm. of sodium glycerophosphate per kilo. The animals were catheterized before, 1/2 hour and 1 hour after injection. The pH of the urine was estimated, and the specimens were analyzed for calcium, and for inorganic and total phosphorus. The serum studies included the determination of alkali reserve, chloride, calcium and inorganic phosphorus. Nine animals were used; 76 injections were made in all. The earlier determinations served to establish the normal resting excretion of calcium and phosphorus, and the duration of the post-injection period which was significant for study.