THE COLORIMETRIC ESTIMATION OF PROTEINS IN VARIOUS BODY FLUIDS

Abstract

In undertaking a study of infantile nephrosis, we were confronted with the problem of having to determine the total protein content and albuminglobulin ratios of numerous specimens of blood, urine, and abdominal fluid. The commonly employed calorimetric (1) and nephelometric (2) methods yielded results in our hands which did not compare favorably with those of the time-consuming micro-Kjeldahl procedure. These circumstances led us to attempt the determination of the proteins in these body fluids in terms of arginine which can be determined directly in whole proteins by means of the Sakaguchi reaction (3). Our experiments disclosed that when alkaline solutions of the protein fractions, obtained by treatment of the specimens with trichloroacetic acid or sodium sulfate solutions of appropriate concentration, were submitted to the modified Sakaguchi reaction (4) arginine values were obtained which when factored gave protein figures closely approximating those secured by the micro-Kjeldahl technique. The ease and rapidity of operation, high degree of accuracy, and diminished sample size required in the new procedure have prompted us to discard the Kjeldahl method for work of this nature.