INVIVO EVIDENCE FOR FUNCTIONAL HETEROGENEITY OF TRANSFERRIN-BOUND IRON .4. SELECTIVE UPTAKE BY ERYTHROID PRECURSORS OF RADIOIRON FROM PORTAL-VEIN PLASMA TRANSFERRIN DURING INTESTINAL IRON-ABSORPTION

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 89  (1) , 51-64
Abstract
The Fletcher-Huehns hypothesis predicts that Fe absorbed by the intestine is delivered selectively to the erythroblast-oriented Fe-binding site of transferrin in portal plasma. This prediction was tested in rats by measuring in vitro the rate and amount of 59Fe taken up by reticulocytes and bone marrow erythroblasts from selectively labeled portal plasma and randomly labeled peripheral plasma. Portal plasma transferrin was significantly more effective than peripheral plasma in delivering 59Fe to both reticulocytes and marrow erythroblasts; on a per-cell basis the erythroblasts took up about 5 times more 59Fe. Fe-deficient reticulocytes were more avid but less discriminating than Fe-replete reticulocytes in uptake of Fe from the 2 plasma sources. When injected into normal test rats in vivo, 59Fe from portal plasma was preferentially removed by red cell precursors and preferentially incorporated into heme extracted from marrow and spleen. These results support the concept of selective release of Fe to erythroblast-oriented binding sites of portal plasma transferrin by intestinal cells during absorption. Combined with previously demonstrated selective tissue uptake of Fe from transferrin, these experiments offer strong support for the active role of transferrin in the rat''s internal Fe exchange.

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