Ittel TH, Kinzel S, Ortmanns A, Sieberth HG
Effect of iron status on intestinal absorption of
aluminum: a reappraisal
(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
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)