Patterns of Vitamin B₁₂ Absorption in Humans Mediated by Homologous and Heterologous Intrinsic Factors

Abstract

Ranlöv, P. & Rask-Madsen. J. Patterns of vitamin B₁₂ absorption in humans mediated by homologous and heterologous intrinsic factor. Scand. J. Gastroent. 1974, 9, 327-334.

The relative potencies of human gastric juice, dried hog pyloric mucosa, purified hog intrinsic factor, and rat gastric juice in the absorption of vitamin B₁₂ were studied in 27 normal subjects and in 6 patients with pernicious anaemia. A paired radiolabel technique was employed by which homologous together with a heterologous intrinsic factor – vitamin B₁₂ complex was administered both orally and via tube directly into the small intestine at various levels. Human and rat intrinsic factors were equally effective in promoting vitamin B₁₂ absorption, regardless of the route of administration. In all subjects investigated significantly less vitamin B₁₂ was absorbed when administered in complex with crude hog intrinsic factor, and the absorptive tendency decreased the more aboral the preparation was instilled. The findings are interpreted in terms of lacking proteolytic action on the non-specific B₁₂ binders in the distal human ileum. For these reasons the merits of continued diagnostic use of hog pyloric mucosa preparations are questioned.

Key-words::

• B₁₂ Absorption
• B₁₂ binders
• hog IF
• human IF
• ileum
• pernicious anaemia
• rat IF
• Schilling test