Regional specificity of iron uptake by small intestinal brush-border membranes from normal and iron-deficient mice.
Fe(II)-ascorbate uptake by purified small intestinal brush-border membrane vesicles prepared from proximal and distal segments was studied in normal and iron-deficient mice. Iron was maintained in a reduced, soluble form by a 20-fold excess of ascorbate at a physiological pH of 7.2-7.4. In normal mice, iron uptake by proximal membrane vesicles was three- to fourfold greater (approximately 1,700 pmol/mg prot) than from distal segments (approximately 500 pmol/mg prot). In iron-deficient mice, uptake of Fe(II) was also greater in proximal membranes (approximately 3,200 pmol/mg prot) than uptake from distal segments (approximately 350 pmol/mg prot), and the regional difference was almost 10-fold, without any change in distal segmental iron uptake. These results are consistent with the pattern of intestinal iron absorption in iron-replete and iron-deficient animals and indicate that regulatory changes in proximal intestinal brush-border membranes may account for the increased iron absorption known to occur in iron deficiency.
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism* / Q000648:ultrastructure; D007501:Iron / Q000378:metabolism*; D000090463:Iron Deficiencies; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008871:Microvilli / Q000378:metabolism
D005296:Ferrous Compounds; D007501:Iron; D001205:Ascorbic Acid