Uropepsin excretion by the human kidney

1. In ten cases the relationship between the excretion of uropepsin and the clearance of endogenous creatinine was studied. In eight cases a direct relationship between the values was found, indicating that uropepsin is excreted in the urine by glomerular filtration. 2. In six cases it was possible to prove that the regression lines did not deviate significantly from zero. In two cases it was not possible to carry out this evaluation owing to the small slope of regression lines, indicating that participation of the renal tubule is not involved. 3. The concentration of uropepsin in the glomerular filtrate was calculated from the relation between the rate of excretion (units per minute) and the glomerular filtration. The average value of the concentration of uropepsin in the glomerular filtrate is 0.52 units per cc.