Urinary protein determination using Coomassie Brilliant Blue in the presence of sodium dodecyi sulphate

Measurement of urinary proteins is a complex problem which has been perfectly described [l]. Bradford’s method [2], which involves binding Coomassie Brilliant Blue G-250 (CBB) to proteins, has been proposed for urinary assay [3,4]. This method appears to be relatively free from interferences I2,3,5]. It has been compared for its advantages with different meth~olo~es, including selected methods (671. Some authors agree with Bradford’s method, applied to urinary proteins [8] and others criticize it, for the lack of precision [9]. Moreover, the wide variation in the sensitivity to various proteins may explain discussions in the choice of the standard for calibration as well as discrepancies in measurement of proteinuria, especially in cases of myelomas, diabetes mellitus and chronic renal failure [6,10,11]. In research applications, two variants of the original Bradford method have been proposed to equalize the differences in the reactivity of CBB: increasing the concentration of CBB dye [12] or adding sodium dodecyl sulphate (SDS) in the reagent [13]. Macart and Gerbaut [14] applied the latter to cerebrospinal fluid (CSF). The aim of this work was to determine if the method described by Macart (CBB-SDS: method B) 1141 presents significant advantages over Bradford’s method (CBB alone: method A) [Z] for urinary protein determination. For this purpose, as a first step, proteinuria was measured by methods A and B automated on an ABA 100 analyser, in samples selected randomly or according to their electrophoretic pattern on SDS-polyacrylamide slabs. Next, we studied the response obtained by both methods assaying urinary proteins fractionated by gel