Role of Urea in Rat Proteinuria

¹ From the Department of Biochemistry, College of Agriculture, University of Wisconsin, Madison, Wisconsin

Dietary casein and soy protein were equally effective in increasing the normal proteinuria of the male rat. Urea fed ad libitum increased proteinuria, but the increase was usually less than that due to an isonitrogenous level of casein. Urea fed 2 hr/day brought on a rapid increase in proteinuria, which over the rest of the day followed neither the blood levels of urea nor the intake of water. An amino acid mixture, prepared to imitate the composition of casein, increased proteinuria to that caused by an isonitrogenous addition of urea but less than that caused by the equivalent high protein diet. Varying the level of vitamin B₆ had no effect on the proteinuria of rats on several different diets. A simplified method for the routine estimation of rat urinary protein by centrifugation is presented.