Abstract
The effect of pancreatic juice on vitamin B_12 absorption was studied in dogs. It was found that dog gastric juice as well as pancreatic juice contain vitamin B_12 binding proteins which differ in the elution pattern on DEAE-cellulose columns, the former being eluted at much lower sodium chloride concentrations. When radio-active vitamin B_12 was fed or instilled in the proximal bowel and vitamin B_12 recovered at different bowel levels, it was found that vitamin B_12-protein complex behaved like gastric juice binder in the proximal bowel and like pancreatic binder in the distal. In vitro digestion of gastric binder with pancreatic juice altered vitamin B_12-protein complex in such a way that elution pattern became similar to that of pancreatic juice. It was also shown that the change was not due to transfer of vitamin B_12 from gastric binder to pancreatic binder. Trypsin digestion had similar effect on gastric binder, and Sephadex G-200 gel-filtration demonstrated reduction in the molecular size. In the dog, vitamin B_12 first bound to gastric binder undergoes chemical changes in the bowel and becomes a readily absorbable form in the distal bowel.
