HDCN Article Review/Hyperlink

Ittel TH, Kinzel S, Ortmanns A, Sieberth HG

Effect of iron status on intestinal absorption of aluminum: a reappraisal

Kidney Int (Dec) 50:1879-1888 1996

It has been suggested that patients with iron deficiency are at risk for aluminum toxicity via enhanced intestinal absorption of aluminum. As serum aluminum is bound to transferrin, one mechanism for increased absorption might be increased expression of transferrin receptors in iron deficiency. However, this mechanism has been questioned because no transferrin receptors are expressed on the absorptive surfaces of intestinal epithelial cells.

Ittel et al studied aluminum absorption in iron-overloaded and iron- deficient 5/6 nephrectomized rats given an oral Al load. Iron status did not affect the degree of tissue Al after Al loading. Similar results were obtained using in situ perfusion/Al loading of intestine in iron- loaded and iron-deficient animals. Mannitol absorption was increased in the uremic rats, suggesting increased paracellular permeability. Pharmacologic blockade of the paracellular pathway using kinetin reduced Al accumulation in uremic (but not in control) rats. The data suggest that absorption of neither iron nor Al is mediated by transferrin receptors, and that Al absorption is not via an iron-specific pathway, but via a paracellular pathway in the intestine.

Comment: Interestingly, citrate also increases intestinal absorption via the paracellular pathway. A nice study which has direct patient care implications. (John T. Daugirdas, M.D., University of Illinois at Chicago)