THE EFFECT OF A FALL IN FILTRATION RATE ON SOLUTE AND WATER EXCRETION IN HYDROPENIC MAN*†

Abstract

Glomerular filtration rate was reduced at least 50% for 1-2 hours in 3 groups of hydropenic subjects. These 3 groups consisted, respectively, of subjects without renal disease on normal salt intakes, similar subjects on salt-free diets treated with salt-retaining hormone, and patients with frank renal failure. In each of the first 2 groups, comparable falls in filtration rate produced decreases in total urine osmolality averaging 10%. In the majority of the subjects with renal failure, a fall in filtration rate produced a slight increase in urine osmolality. In all 3 groups, the fall in filtration rate was associated with a marked drop in the rate of water and salt excretion, but with a lesser fall in the rate of K excretion.