Immunochemical Study on Rat Urinary Proteins: Their Relation to Serum and Kidney Proteins (Chromatographic Separation of the Major Urinary Protein)

Abstract

Summary After agar electrophoresis, only two protein bands migrating in the albumin and α2-globulin zones have been revealed in rat urine. However, by immunoelectrophoretic analysis, the presence of at least 10 proteins has been demonstrated in rat urine. Half of them derived from the serum; the other proteins, the specific urinary proteins, probably originated from the urinary tract. Their relative electrophoretic mobilities compared to rat serum albumin mobility were as follows: 1.16, 1.09, 1.02, 0.68 and 0.64. The last, which was also the strongest antigen, has been designated by us the rat major urinary protein. Double diffusion in agar gel has demonstrated its antigenic identity with renal constituent. The major urinary protein isolated by chromatography on diethylaminoethyl (DEAE)-cellulose had the following analysis: nitrogen, 10.3%; hexose, 2.2%. Its diffusion coefficient determined by double diffusion in gel was equal to 7.2 × 10-7 cm2 sec-1. The isoelectric point was at pH 2.1 in 0.1 M phosphate buffer. The origin of specific urinary proteins and their possible physiopathologic role in nephrotic syndromes have been discussed. The presence of a species-specific major protein in the urine of mammals has also been suggested.