A RENAL REABSORPTIVE MECHANISM IN THE DOG COMMON TO GLYCIN AND CREATINE

Abstract

The renal tubular reabsorption of amino nitrogen in the dog was assessed at various arterial plasma levels obtained by the infusion of glyein. Amino nitrogen was reabsorbed by an active mechanism which exhibited a limitation of transfer capacity. The maximal rate of reab-sorption was attained rather gradually and as a consequence no sharp renal threshold existed. Creatine was reabsorbed by the same system. Competition between creatine and amino nitrogen for a common link in the reabsorptive chain brought about a reduction in the amt. of creatine reabsorbed at elevated plasma amino nitrogen levels. As a result of this competition for a common renal reabsorptive mechanism studies of creatine precursors based on feeding amino acids and the measurement of excess creatine eliminated in the urine are rendered suspect.