Non-haem iron transport in the rat proximal colon.
BACKGROUND
Only 10% of dietary iron is absorbed in the duodenum which implies that 90% (approximately 9 mg day(-1)) reaches the lower small intestine and colon. Therefore the purpose of this study was to assess the iron transport capacity of the rat proximal colon and to determine whether iron absorption is regulated by changes in dietary iron content.


METHODS
Rats were fed for 14 days on either iron adequate (44 mg Fe kg(-1) diet) or iron-deficient (< 0.5 mg Fe kg(-1) diet) diets. The 59Fe transport across the colonic epithelium and its subsequent appearance in the blood were measured in vivo. In separate studies the colon was excised and used to measure divalent metal transporter expression.


RESULTS
Divalent metal transporter (DMT1) was expressed at the apical membrane of the surface epithelium in rat proximal colon. In animals fed an iron-deficient diet, DMT1 mRNA and protein expression were increased. This was accompanied by a significant increase in tissue 59Fe uptake.


CONCLUSIONS
The proximal colon can absorb non-haem iron from the intestinal lumen. The purpose of this mechanism remains to be elucidated.
Johnston
K L
KL
School of Biomedical & Molecular Sciences, University of Surrey, Guildford, UK.
Johnson
D M
DM
Marks
J
J
Srai
S K
SK
Debnam
E S
ES
Sharp
P A
PA
D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000378:metabolism; D003106:Colon / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism; D006418:Heme; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007501:Iron / Q000097:blood; D000090463:Iron Deficiencies; D019266:Iron, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics*; D033862:Iron-Binding Proteins / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D000099236:Solute Carrier Family 11, Member 2
D027682:Cation Transport Proteins; D006418:Heme; D007501:Iron; D019266:Iron, Dietary; D033862:Iron-Binding Proteins; D000099236:Solute Carrier Family 11, Member 2