Release of Vitamin B 12 and Cobamide Coenzyme from Rat Intrinsic Factor by Rat Intestinal Extracts.

Abstract

Summary

The ability of rat intestinal extracts to release Vit. B₁₂Co⁶⁰ bound to rat intrinsic factor extract was studied using equilibrium dialysis. The small intestines of adult rats were divided into 10 equal segments and extracts of each segment were prepared. Releasing factor activity was detected in all the segments but 2 peaks of activity were found in the proximal area (segment 1) and the mid-portion of the small intestine (segments 4, 5 and 6). Releasing factor activity of the proximal and mid-portion was partially inactivated by heat. Sodium fluoride, sodium arsenite, potassium cyanide or 2,4-dinitrophenol at 10^-2 M did not markedly inhibit the releasing factor activity. The same anatomical distribution of releasing factor activity was observed with 5,6-dimethylbenzimidazolyl cobamide coenzyme bound to rat intrinsic factor. The finding of releasing factor activity in the midgut is consistent with observations on the site of absorption of Vit. B₁₂ in the rat.