Intrinsic factor-mediated binding of cyanocobalamin to cholestyramine

The intrinsic factor-mediated binding of cyanocobalamin to cholestyramine was studied in vitro under varying conditions of pH, added electrolyte, and bile salt. The intrinsic factor-cyanocobalamin complex was adsorbed strongly by the resin at pH 3 in the presence of neutral salt and low concentrations of glycocholic acid. An increase in glycocholic acid concentration as well as neutral pH decreased the observed binding, although significant amounts of cyanocobalamin-intrinsic factor complex remained bound after incubation at pH 6.8. Cyanocobalamin alone was not adsorbed by the resin.