Protein-Bound Sterols in Rodent Urine

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

Normal rats excreted an average of about 15 µg of cholesterol in the urine daily plus 2 µg of a fast-acting sterol; mice, 2 µg and 0.2 µg, respectively. Chromogenic, chromatographic and chemical evidence suggested the fast-acting sterol to be ⁷-cholestenol. The sterols of rat urine were bound to both albumin and globulin, cholesterol being more concentrated in the globulin fraction. The excretion of cholesterol varied with age, sex, species, and strain; it could be increased greatly by injecting ⁷-cholestenol, somewhat by injecting cholesterol or by feeding a high fat diet, and very slightly by feeding a high protein diet; it was not altered by high dietary cholesterol, by glomerulonephritis due to N,N'-diacetylbenzidine, nor by the presence of a hepatoma. The urinary cholesterol of the rat was 74% unesterified; the fast-acting sterol, 24%. Six to eleven per cent of the total sterol of rat and mouse bladder was found to be fast-acting, all bladder sterol being unesterified.