Determination of the R-protein and the R-protein-vitamin B12-complex in saliva and gastrointestinal juice by FPLC Mono S cationic chromatography

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Abstract
The binding of vitamin B12 to the two vitamin B12 binding proteins—intrinsic factor and R-protein—in gastrointestinal juice is pH dependent. It is therefore of importance that binding studies are carried out at pH values near the physiological pH of the gastric juice. In the present study the vitamin B12 complexes of the two vitamin B12 binders were separated at a pH of 1.8 using the cationic exchange chromatograph Mono S attached to the fast protein liquid chromatography (FPLC) system. The R-protein concentration was measured in saliva and gastric juice with high accuracy and with highly significant correlation compared to the serum-coated charcoal method of Gottlieb. The method showed a decreased recovery in duodenal juice and in samples with high bile content.