THE UPTAKE OF ALUMINUM AND ITS EFFECT ON IRON-METABOLISM IN THE OSTEOBLAST-LIKE CELL-LINE MG-63

Accumulation of aluminum (Al) in the bone is a well-known complication of hemodialysis, but the mechanism of uptake of Al by the bone is poo rly understood. Using the osteoblast-like cell line MG-63 it was found that the iron-transport protein transferrin facilitated Al-uptake in a dose-dependent manner. Uptake of Al from AlCl3 or Al-citrate was muc h lower and not dose-dependent. During an 8 h incubation Al-transferri n inhibited uptake of iron from Fe-59-transferrin, but no such inhibit ion occurred if the cells were preincubated with Al-transferrin for 64 h before pulsing with Fe-59-transferrin. It is proposed that Al initi ally down-regulates cellular iron uptake mechanisms, but that these re vert to normal as the cells become iron-deficient and/or loaded with A l. These results suggest that transferrin may act as the physiological carrier of Al to the bone, and that Al may affect iron uptake and met abolism in bone.