Enhancement by human bile of the binding of free and intrinsic factor-bound cobalamin (vitamin B12) to small bowel epithelial cell receptors.Am J Gastroenterol. 1985 Dec; 80(12):964-9.AJ
The effect of human bile on the binding of free cobalamin (Cbl) and of intrinsic factor-Cbl (IF-Cbl) complexes to intestine receptors was examined in in vitro receptor extracts made from guinea pig small bowel epithelial cells. Cbl and IF-Cbl complex binding to the receptors was measured in the effluent from a Sephadex G-200 column. Intrinsic factor-Cbl binding to the receptors in the control samples was 4.32 +/- 0.07 ng/animal (mean +/- SEM); addition of bile, saturated with excess 57Co-Cbl enhanced binding to 5.26 +/- 0.16 ng/animal (p less than 0.001). These data suggest that bile enhances binding of IF-Cbl complex onto ileal receptors. Whether bile also serves as "releasing factor" by releasing Cbl from intrinsic factor in vivo remains to be determined.