Effect of bile and bile acids on binding of intrinsic factor to cobalamin and intrinsic factor-cobalamin complex to ileal receptor.
Effect of bile and bile acids on binding of intrinsic factor to cobalamin and intrinsic factor-cobalamin complex to ileal receptor.
复制标题
胆汁和胆汁酸对内因子与钴胺素以及内因子-钴胺素复合物与回肠受体结合的影响。
DOI：
10.1152/ajpgi.1983.245.1.g72
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Alpers,DH
中科院分区：
文献类型：
--
作者：
Seetharam,B;Jimenez,M;Alpers,DH
人胆汁或市售胆汁酸与[57Co]钴胺(Cbl)结合是因为存在“R”型结合剂，前者通常存在，后者则作为污染物存在。这些R蛋白竞争Cbl与内源性因子(IF)的结合可以解释先前归因于胆汁酸本身的体内抑制作用。R蛋白似乎参与了Cbl结合的抑制，因为酶消化胆汁或胆汁酸都会取消Cbl的结合能力。此外，R蛋白的抗体可消除这种抑制作用。胆汁或胆汁酸对纯化的If或If-Cbl受体分子没有直接影响，即使胆汁酸增加了If-[57Co]Cbl与回肠刷状缘膜的附着。这些数据表明胆汁成分可能影响Cbl吸收的两个步骤：Cbl与IF和IF-Cbl与其回肠受体的结合。目前尚不清楚这些体外现象对Cbl在体内的正常吸收是否重要。
Human bile or commercially available bile acids bind [57Co]cobalamin (Cbl) due to the presence of "R"-type binders, which are normally 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.