Gene expression of divalent metal transporter 1 and transferrin receptor in duodenum of Belgrade rats

Regulation of iron absorption is thought to be mediated by the amount of ir on taken up by duodenal crypt cells via the transferrin receptor (TfR)-tran sferrin cycle and the activity of the divalent metal transporter (DMT1), al though DMT1 cannot be detected morphologically in crypt cells. We investiga ted the uptake of transferrin-bound iron by duodenal enterocytes in Wistar rats fed different levels of iron and Belgrade (b/b) rats in which iron upt ake by the transferrin cycle is defective because of a mutation in DMT1. We showed that DMT1 in our colony of b/b rats contains the G185R mutation, wh ich in enterocytes results in reduced cellular iron content and increased D MT1 gene expression similar to levels in iron deficiency of normal rats. In all groups the uptake of transferrin-bound iron by crypt cells was directl y proportional to plasma iron concentration, being highest in iron-loaded W istar rats and b/b rats. We conclude that the uptake of transferrin-bound i ron by developing enterocytes is largely independent of DMT1.