Cellular localization of divalent metal transporter DMT-1 in rat kidney

We have demonstrated that the kidney plays an important role in iron balanc e and that metabolically significant reabsorption of this ion occurs in the loop of Henle and the collecting ducts [Wareing M, Ferguson CJ, Green R, R iccardi D, and Smith CP. J Physiol (Lond) 524: 581-586, 2000]. To test the possibility that the divalent metal transporter DMT1 (Gunshin H, Mackenzie B, Berger UV, Gunshin Y, Romero MF, Boron WF, Nussberger S, Gollan JL, and Hediger MA. Nature 388: 482-488, 1997) could represent the apical route for iron entry in the kidney, we raised and affinity-purified an anti-DMT-1 po lyclonal antibody and determined DMT-1 distribution in rat kidney by Wester n analysis, immunofluorescence, and confocal microscopy. The strongest DMT1 -specific (i.e., peptide-protectable) immunoreactivity was found in the col lecting ducts, in both principal and intercalated cells. Thick ascending li mbs of Henle's loop and, more intensely, distal convoluted tubules exhibite d apical immunostaining. Considerable intracellular DMT-1 immunoreactivity was seen throughout the nephron, particularly in S3 segments. The described distribution of DMT-1 protein is in agreement with our previous identifica tion of nephron sites of iron reabsorption, suggesting that DMT-1 provides the molecular mechanism for apical iron entry in the distal nephron but not in the proximal tubule. Basolateral iron exit may be facilitated by a diff erent system.