Urinary proteins in Sprague-Dawley rats with chronic progressive nephrosis

By means of polyacrylamide concentration and electrophoresis on cellulose acetate strips, protein fractions have been determined in the urine of male Sprague-Dawley rats from 6 1/2-28 mo of age. An increasing percentage of albumin was expressed in the albumin/globulin ratios of 0.72, in a group of rats excreting a mean concentration of 1.91 mg/ml of protein in the urine, and 2.24 in a group of rats excreting, on the average, 17.62 mg/ml. A relative decrease in globulin, particularly of the alpha2 fraction, was shown. From a statistical model based on the regression parameters for 24-hr protein excretion and urine protein concentration, it was estimated that the doubling time for protein excretion was 3.2-3.69 mo. This interval is roughly one-half that reported for the Wistar rat.