Renal Tubular Regulation of Urea Excretion in Man

Publisher Website
Google Scholar
Abstract
Adult male subjects were studied on a normal protein diet and on a low protein diet (basic rice diet with salt and fat supplements). Simultaneous inulin and urea clearances and total solute excretion were determined at high and low rates of urine flow on both diets. The glomerular filtration rate (GFR) was not altered by the low protein intake with salt added to the diet. After 5 weeks of low protein intake there was a marked decrease in the fraction of filtered urea excreted at low urine flows. This difference was not apparent during maximal water diuresis (inulin U/P < 15). At lower rates of urine flow (inulin U/P > 15) the fraction of filtered urea excreted at any given rate of urine flow was less than that found during normal protein intake. This difference increased at progressively lower rates of urine flow. The decrease in the fraction of filtered urea excreted during low protein intake was apparently not caused by changes in the rate of urine flow, GFR, plasma urea concentration, or total solute excretion. These findings indicate renal tubular regulation of urea excretion in man of a nature similar to that found in other mammals. Submitted on April 14, 1958