Presence in Milk of the Extrinsic Factor of Castle

Abstract

The extrinsic factor of Castle has been found in several protein-containing foods, such as beef muscle, 1 autolyzed yeast, 2 wheat germ, 2 and egg white. 3 From Castle's 4 more recent work, one may infer that some of the negative results obtained with protein foods other than these, were due to prolonged incubation periods, or the trial use of the materials at hydrogen ion concentrations too great for the interaction of the extrinsic and intrinsic factors. Casein 5 has been reported as giving a negative response at a pH of 2.5 to 3.5, however, more recently Taylor, et al., 6 have indicated that the intrinsic factor is an enzyme which has optimum action at pH 7.4 to 7,7. Because infants may be fed on whole milk alone for long periods of time without developing pernicious anemia, it would seem possible that milk which contains Caseinogen as the greatest part of its protein might contain the extrinsic factor. Because of this we have investigated the value of milk as a source of extrinsic factor with 2 pernicious anemia patients, and to 3 patients with pernicious anemia we have given partitions of milk with gastric juice to see if the extrinsic factor were contained in the whey.

All of these patients presented classical signs of pernicious anemia, 2 had had previous relapses and although 2 were negroes, all, subsequent to the experiments, have gone into remissions on liver therapy. The diets used were high in carbohydrates and lacking in meat, eggs, and whole cereals, while the patients were receiving experimental material. In Case 1, however, the patient prior to the experiment received a diet rich in meat to rule out dietary deficiency.