Weintraub L R, Weinstein M B, Huser H J, Rafal S
J Clin Invest. 1968 Mar;47(3):531-9. doi: 10.1172/JCI105749.
The dog behaves like man in his ability to utilize dietary hemoglobin iron and, therefore, is an excellent model in which to study the mechanisms of absorption. Heme is taken up intact into the epithelial cell of the small intestine but the iron appears in the plasma in a nonheme form. A substance is present in mucosal homogenates which is capable of releasing iron from a hemoglobin substrate in vitro. This has a molecular weight greater than 64,000, and appears to behave as an enzyme. There is no difference in the in vitro, effective concentration of the hemesplitting substance in the mucosa of iron-loaded and iron-deficient dogs to explain in vivo changes in iron absorption. However, the rate at which the heme-splitting substance works in vivo appears to be increased by the removal of the nonheme-iron-end product from the epithelial cell to the plasma. Reduction of the heme-iron content within the epithelial cell may then enhance uptake from the lumen. These studies suggest that the labile nonheme-iron content of the intestinal epithelial cell determines its ability to accept heme as well as ionized iron from the lumen.
狗在利用膳食血红蛋白铁方面的能力与人类相似，因此是研究铁吸收机制的优秀模型。血红素以完整的形式被小肠上皮细胞摄取，但铁以非血红素形式出现在血浆中。黏膜匀浆中存在一种物质，它能够在体外从血红蛋白底物中释放铁。这种物质的分子量大于64,000，似乎具有酶的特性。铁负荷和缺铁犬的黏膜中，血红素分解物质的体外有效浓度没有差异，无法解释体内铁吸收的变化。然而，通过将非血红素铁终产物从上皮细胞转运到血浆中，血红素分解物质在体内发挥作用的速率似乎会增加。上皮细胞内血红素铁含量的降低可能会增强从肠腔的摄取。这些研究表明，肠道上皮细胞中不稳定的非血红素铁含量决定了其从肠腔接受血红素以及离子化铁的能力。
