THE EXCRETION OF UREA IN NORMAL MAN AND IN SUBJECTS WITH GLOMERULONEPHRITIS 1

Abstract

The urea clearance was examined in 10 normal subjects and 22 subjects with glomerulonephritis, with special reference to the degree of conc. of the glomerular filtrate as indicated by the simultaneous inulin U/P ratio. Urea is invariably reabsorbed to some extent from the glomerular filtrate, whether this is at the normal level or is reduced by disease. Water reabsorption occurs in 2 stages, one in the proximal tubule and one in the thin limb and distal tubule. At any inulin U/P ratio the reabsorption of urea proceeds in the nephritic kidney essentially as it would in the normal kidney. As the capacity to reabsorb water is impaired by disease. the fraction of urea reabsorbed decreases, so that the urea clearance approaches the rate of glomerular filtration. In none of the subjects examined was there evidence of increased back-diffusion of urea, the elevation of the blood urea in nephritis being a result solely of the reciprocal relationship between this term and the urea clearance, as expected in principle.