Enhanced Vitamin B 12 Absorption from Rat Intestine by Proteases In the Absence of Intrinsic Factor

Summary

Rat liver containing radioactive B12 in its natural form was prepared by repeated injections of Co⁵⁷-hydroxocobalamin and absorption of liver bound B₁₂ was investigated using isolated rat intestine in vivo.

There was no indication for the production of readily absorbable forms of B₁₂ complex during digestion with trypsin, chymotrypsin, papain, pepsin and Pronase. It was found that Pronase, a potent Streptomyces proteases preparation, increased absorption of liver bound B₁₂ as well as free B₁₂ in the absence of IF, the increase being comparable to that obtained with IF under the same condition. This effect was demonstrable only when Pronase was placed in the isolated intestine in large quantities. These results suggest a possible relationship of intestinal digestion to the absorption mechanism of B₁₂ which involves IF.