Evidence for intestinal origin of transcobalamin II during vitamin B,2absorption

Abstract

The plasma binding of newly absorbed, radioactively labelled vitamin B12was studied during a urinary excretion (Schilling) test. Vitamin B12, after being absorbed from the gut, enters blood attached to transcobalamin II, which seems to be derived from the ileal enterocyte. The absorbed B12re-enters the blood stream after the transcobalamin II-B12complex is cleared by the liver and it is then excreted into the urine during the Schilling test. © 1978, British Medical Journal Publishing Group. All rights reserved.