THE RENAL EXCRETION OF INORGANIC PHOSPHATE IN RELATION TO THE ACTION OF VITAMIN D AND PARATHYROID HORMONE 1

Abstract

The renal clearances of creatinine and phosphate were detd. simultaneously in dogs following the intraven. inj. of Na phosphate. It was possible to estimate the reabsorption of phosphate by the renal tubules. There was a limiting maximal rate of renal tubular reabsbrption of phosphate; phosphate filtered through the glomeruli in excess of this maximum reabsorptive capacity was excreted in the urine. The maximal rate of renal tubular reabsorption of phosphate was reduced in young dogs fed rachitogenic diets. A prompt increase was observed following the adm. of vit. D. The inj. of parathyroid extract decreased the rate of renal tubular reabsorption of phosphate. The increase in conc. of phosphate in the blood plasma following vit. D adm., and the decrease following parathyroid hormone, might be explained by the effects of these substances on renal tubular reabsorption of phosphate.