Intestinal distribution of intrinsic factor and vitamin B₁₂ absorption

¹ Department of Medicine, Kurume University School of Medicine, Kurume, and Department of Medicine, Yamaguchi Medical College, Ube, Japan

Evidence is presented that intrinsic-factor (IF) activity is present in the small intestine as far down as the ileal end. Physiologic doses of radioactive vitamin B₁₂ without IF were applied directly into various levels of the intestine by surgical and other means in man and rats, and significant absorption was obtained from the small intestine. Absorption inhibition by ethylenediaminetetraacetate and its counteraction by Ca ion demonstrated that such absorption was dependent on IF action. The large intestine was shown to be incapable of physiologic absorption of vitamin B₁₂, and IF was totally ineffective. It is proposed that physiologically, gastric IF descends with some activity in the small intestine, where more of the food vitamin B₁₂ is liberated by digestion and subjected to IF.

Key Words: small intestine • cecum • colon • intestinal loop • technique • Schilling test • ethylenediaminetetraacetate • calcium ion

Submitted on April 16, 1964