Effect of bile and bile acids on binding of intrinsic factor to cobalamin and intrinsic factor-cobalamin complex to ileal receptor

B. Seetharam, M. Jimenez, D. H. Alpers

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Abstract

Human bile of commercially available bile acids bind [57Co]cobalamin (Cbl) due to the presence of 'R'-type binders, which are probably present in the former and present as a contaminant in the latter. The competition of these R proteins for the binding of Cbl by intrinsic factor (IF) could explain the in vivo inhibition attributed previously to the bile acids themselves. R protein seems to be involved in the inhibition of Cbl binding because protease digestion of either bile or bile acid abolishes the Cbl binding ability. Moreover, antibody to R protein abolishes the inhibition. Bile or bile acids do not have a direct effect on either purified IF or the IF-Cbl receptor molecule, even though bile acids increase the attachment of IF-[57Co]Cbl to ileal brush-border membranes. These data demonstrate two steps where components of bile could affect Cbl absorption: the binding of Cbl to IF and of IF-Cbl to its ileal receptor. It is not clear whether these in vitro phenomena are important for the normal absorption of Cbl in vivo.

Original languageEnglish
Pages (from-to)G72-G77
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume8
Issue number1
StatePublished - Jan 1 1983

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