A modified method for determination of uropepsin.

T HAS BEEN NOTED by several authors that in uropepsin determination a major proportion of the total activity is due to conversion of pepsinogen to pepsin, whereas a small proportion of the activity obtained is due to some system other than pepsin. As a result of this, in the quantitative determination of uropepsin some specimens give results which are erroneously high. Several methods for determination of pepsinogen in the urine (uropepsin) have been described in which hemoglobin substrate has been used as a suitable protein (1-4). The digested hemoglobin is estimated by the blue color reaction with phenol reagent (FolinCiocalteu) (5). The intensity of this color is dependent upon the tyrosine-like substances resulting from proteolysis. However, as described above, there also develops a color that interferes with the true results. For confirmation of this interference the following study of urine has been conducted. The urine specimen was heated to 80#{176} for 15 minutes to destroy the enzymes (6-9).. Then, after addition of hydrochloric acid to pH 1.5, the determination was made by the Gray, Ramsey, Reifenstein method (3). In 23 cases out of 70 (32.8 per cent), it was observed that the developed blue color with phenol reagent was darker in the incubated than in the unincubated tube, whereas it should have been identical, considering that the enzyme action had been excluded by the preliminary heating of the specimen. Analogical results were obtained with other specimens that were boiled for 3 minutes previous to acidification to pH 1.5 (6). Dark-