[Determination of urinary total proteins and some protein fractions]

In unconcentrated specimens measurements have been made of total proteins, by DOETSCH gel-filtration method, and of albumin, transferrin and of alpha-2-macroglobulin, by LAURELL electroimmunodiffusion technique. The results confirm that the gel-filtration method provides specific, reliable measurement of proteins in amount as little as 50 mg/1. The proteinuria of 21 samples of urine has been determined by the DOETSCH method and by the biuret method after protein precipitation by perchloric, trichloracetic and phosphotungstic acid. Only the use of phosphotungstic acid as precipitant provides a good correlation of results between the biuret method and the direct gel-filtration-biuret method. LAURELL electroimmunodiffusion technique was improved to allow the determination of 5 mg/1 of albumin, and transferrin, and of 1 mg/1 of alpha-2-macroglobulin. The AA. emphasize the advantages of using sensitive methods which do not require the preliminary concentration of the sample, for the analysis of urinary proteins.