The role of membrane-associated iron-binding complex in intestinal iron absorption in the rat

• Published in: Journal of nutritional science and vitaminology 1994-12, Vol.40 (6), p.511-522
• Main Authors: Orimo, H. (Nippon Medical School, Tokyo (Japan)), Hisayasu, S, Hirai, Y, Yoshino, Y
• Format: Article
• Language: English
• Subjects: ABSORCION DIGESTIVA; ABSORPTION DIGESTIVE; Animals; Biological and medical sciences; Blotting, Western; Carrier Proteins - chemistry; Carrier Proteins - isolation & purification; Carrier Proteins - metabolism; Cell Membrane - metabolism; CELL MEMBRANES; Centrifugation, Density Gradient; Chromatography, Gel; DIGESTIVE ABSORPTION; Edetic Acid - pharmacology; Electrophoresis, Polyacrylamide Gel; FER; Ferritins - metabolism; Fundamental and applied biological sciences. Psychology; HIERRO; INTESTIN; Intestinal Absorption; Intestine. Mesentery; INTESTINES; INTESTINOS; IRON; Iron - metabolism; Iron Radioisotopes; Iron-Binding Proteins; Kinetics; Male; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; Molecular Weight; RAT; RATA; RATS; Rats, Wistar; Transferrin - isolation & purification; Transferrin - metabolism; Transferrin-Binding Proteins; Vertebrates: digestive system
• ISSN: 0301-4800; 1881-7742
• DOI: 10.3177/jnsv.40.511

A membrane-associated iron-binding complex was isolated from rat intestinal mucosa during iron absorption. Two 59Fe peaks (peaks 1 and 2) were separated on Sepharose 6B gel filtration from detergent solubilized 20,000 x g precipitate of upper intestinal mucosal homogenate after administration of 59Fe-labelled ferrous materials. Peak 1 was a membrane iron-binding complex whose apparent molecular weight was over 10(6) Da estimated by gel filtration, while peak 2 was identified as ferritin. Three major bands were detected on SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of peak 1. The treatment of mucosal homogenate with 5 mM ethylenediaminetetraacetic acid released 59Fe binding from peak 1. Incorporation of 59Fe to peak 1 showed the maximum at 1 h and then reduced, while [59Fe]ferritin showed reciprocal behavior, which suggested that peak 1 may be a rapid turnover iron pool and transfer 59Fe to ferritin. Peak 1 was also isolated from the brush border membrane and showed similar SDS-PAGE pattern to that from the 20,000 x g precipitate of mucosal homogenate. Western blot analysis did not reveal immunoreactive transferrin in peak 1. Those findings suggest that peak 1 may be a non-ferritin, non-transferrin iron-binding complex located on the brush border membrane and accept iron from the intestinal canal during iron absorption.