OBSERVATIONS ON THE ETIOLOGIC RELATIONSHIP OF ACHYLIA GASTRICA TO PERNICIOUS ANEMIA. VII. RESEMBLANCES BETWEEN THE PROTEOLYTIC ACTIVITY OF NORMAL HUMAN GASTRIC JUICE ON CASEIN IN NEUTRAL SOLUTION AND THE ACTIVITY OF THE INTRINSIC FACTOR 1

Abstract

Incubation at pH 7.4 of normal human gastric juice with 1% casein soln. caused progressive increases in N in trichloracetic acid filtrates. This activity resembled that of the so-called intrinsic factor of normal human gastric juice in that it was (a) independent of the presence of saliva and of regurgitated duodenal contents: (b) absent or greatly diminished in gastric secretion of patients with addisonian pernicious anemia; () not destroyed by Berkefeld filtration or exposure to alkali; (d) destroyed by temps. of 40[degree]C. or above; and (e) inhibited by a medium more acid than pH 3.5. Lloyd''s reagent completely removed the activity. Hydrolysis of casein by the gastric juice at 37.5[degree]C. and pH 7.4 progressed within 24 hrs. chiefly to the stage of proteoses and peptones, as determined by a modification of the nitrogen partition method of Wasteneys and Borsook. Proteolysis was considered not due to pepsin because not significantly affected by exposure to alkali and thereafter was maximal at about pH 8 and absent at pH 2.5. It was considered not due to tryptic- or ereptic-like enzymes because not significantly affected by exposure to alkali, and thereafter activity was observed at both pH 5 and pH 7.4 and relatively little amino N was produced. The possibility that the hydrolysis described is due to the action of the so-called intrinsic factor was discussed.