Abstract
The determination of urinary proteins raises many problems since several requirements, which are difficult to reconcile, have to be satisfied. The method used must be extremely sensitive as normal urine is the biological fluid which contains the least protein and yet not be subject to interference due to urinary pigments, drugs and their metabolites. Furthermore, it should resist great variations in pH or salt content and should also be specific, measuring with equal sensitivity plasma or tissue protein but not amino acids or peptides. Most of the recent literature deals with routine methods [l] and restricts the study of the sensitivity of diverse urinary proteins to commercial albumin and globulin, without taking into account the electrophoretic and clinical classification of proteinurias [2-31. Moreover, correlation studies are often performed with other routine methods and not with a reference method, although several have been proposed [4-81. The aim of this work was to determine whether the Coomassie Brilliant Blue (CBB) method, which has been shown to be equally sensitive to various cerebrospinal fluid proteins by the addition of sodium dodecyl sulfate (SDS) to the reaction (CBB-SDS method) [9,10], could be applied to urinary proteins as well. The study comprises two successive steps. The first is the collection of a variety of well-defined urinary proteins, their purification and fractionation, and comparison of their reactivity with the CBB-SDS and biuret methods. The second step includes a prospective study of urine from healthy subjects and urine samples chosen for their weak proteinuria and high content in pigments and drugs, and comparison of the results obtained with the proposed method and an ultrafiltration biuret method based on Rice [8].
Published Version
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