The absorption of free vitamin B12 and R protein-bound vitamin B12 in the diagnosis of pancreatic exocrine insufficiency in rats.

Vitamin B12 (B12) absorption was studied in rats following biliopancreatic duct ligation. The absorption of free B12, as well as of hog R protein-bound B12, was markedly impaired after both intragastric and intraduodenal administration in these rats. The intraduodenal administration of a mixture of pancreatic extract and sodium bicarbonate (NaHCO3) improved the absorption of both free and R protein-bound B12. However, pancreatic extract without NaHCO3 was ineffective in this respect. Intraduodenal administration of NaHCO3 without pancreatic extract worsened the R protein-bound B12 absorption. This finding would indicate that the degradation of R protein by proteolytic enzymes, in the intestine of rats with pancreatic juice exclusion, is inhibited by NaHCO3.