Correction of Cobalamin Malabsorption in Pancreatic Insufficiency with a Cobalamin Analogue that Binds with High Affinity to R Protein but not to Intrinsic Factor: IN VIVO EVIDENCE THAT A FAILURE TO PARTIALLY DEGRADE R PROTEIN IS RESPONSIBLE FOR COBALAMIN MALABSORPTION IN PANCREATIC INSUFFICIENCY

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Abstract

In vitro studies indicate that [57Co]cobalamin (Cbl) is preferentially bound to salivary R protein as opposed to intrinsic factor (IF) and that [57Co]Cbl bound to R protein is not transferred to IF at either pH 2 or pH 8. Incubation of R protein-[57Co]Cbl with pancreatic proteases causes a partial degradation of the R protein moiety and a rapid transfer of [57Co]Cbl to IF. We have postulated that the etiology of Cbl malabsorption in pancreatic insufficiency is an inability to partially degrade R protein because of a lack of pancreatic proteases. We have tested this hypothesis by determining the ability of a nonradioactive Cbl analogue, bound with high affinity by R protein but not by IF, to correct the malabsorption of [57Co]Cbl in patients with pancreatic insufficiency.

Authors

Robert H. Allen, Bellur Seetharam, Nancy C. Allen, Elaine R. Podell, David H. Alpers