A Simplified Method for the Determination of Pepsinogen in Blood and Urine

A simplified method for the determination of pepsinogen in blood and urine has been developed using serum protein as substrate. As crystalline pepsin digests human serum protein optimally in the region of pH 2, and blood exhibits such proteolytic activity on its own serum protein in this region, the determination of pepsinogen in blood is performed at this pH. The proteolytic activity of serum or plasma on its own (autologous) serum protein is inactivated by alkalinization. The blood of gastrec-tomized patients showed extremely low proteolytic activity in the region of pH 2 by the present method, indicating an absence of pepsinogen. The present method has greater specificity and accuracy than the method employing either hemoglobin or casein as substrate. S INCE Sorenseml (1), Mi.chaelis and Mendelssohn (2), and Northrop (3) found that purified pepsin digests proteins iii vitro optimally in the region of pH 2, a number of physiologic and chemical studies of pepsin have been reported. In 1924, Gottlieb (4) developed an assay method for the determination of pepsinogen in blood and urine. In 1932, Anso