Enhancement by human bile of the binding of free and intrinsic factor-bound cobalamin (vitamin B12) to small bowel epithelial cell receptors.
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.
D000818:Animals; D001646:Bile / Q000378:metabolism*; D004848:Epithelium; D006168:Guinea Pigs; D007421:Intestine, Small / Q000378:metabolism*; D007437:Intrinsic Factor / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D018000:Receptors, Peptide; D014805:Vitamin B 12 / Q000378:metabolism*
D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; C028199:intrinsic factor receptor; D007437:Intrinsic Factor; D014805:Vitamin B 12