Abstract
Summary and Conclusions
1) This article reports some observations on the general nature of vit B12 binding by gastric juice and certain other biologic substances. The majority of vit B12 molecules bound by gastric juice did not dissociate in the presence of excess vitamin molecules added subsequently. 2) Our data show competition offered by certain vit B12 analogues for the cyanocobalamin binding sites of gastric juice, intrinsic factor concentrate, saliva, colostrum, and serum. Of these substances, gastric juice exhibited the greatest preference for cyanocobalamin in the presence of excess analogue. The intrinsic factor concentrate tested was much less fastidious than gastric juice. Saliva, colostrum, and serum exhibited little selectivity in their B12 binding mechanisms. 3) Occurrence of a sulfate, nitrate, or chloride ion in lieu of the cyanide ion in the cobalamin did not diminish competition for cyanocobalamin binding sites of gastric juice.
