The Isolation and Electrophoretic Characterization of the Proteins in the Urine of Normal Subjects1

Abstract

Methods for concentrating proteins from dilute solutions are described and their limitations are discussed. Alcohol precipitation was found to give the best recoveries and most consistent results. Proteins in normal urines were isolated by alcohol precipitation and characterized by Tiselius electrophoresis. Protein components were found in urine having mobilities similar to those of albumin and globulins of serum. The preponderant "globulin" fraction of urine had an electrophoretic mobility similar to that of alpha globulins serum. "Globulins" in urine showed marked heterogeneity. The A/G ratio for urinary proteins was found to be 0.65. The average protein output in the urine of normal individuals was considered to be as high as 90 mg/day. Experiments with I131 tagged human serum albumin injected in 2 normal subjects showed that serum albumin was excreted in normal urines. Paper electrophoresis was shown to be a useful method for the study of the electrophoretic patterns of proteins in small aliquots of normal urine.