Binding and transport of aluminum by serum proteins

摘要

There is a broad consensus that most of the aluminum in serum is bound to protein. A series of ultrafiltration studies indicate that about 85%-90% of the aluminum in normal serum is protein bound. This percentage drops to about 80% in uremic serum. It appears that most, if not all, of this aluminum is bound to the iron transport protein transferrin, which has an aluminum binding constant of about 10~(13). The Al-transferrin complex binds to the transferrin receptor, and receptor-mediated cellular uptake appears to be an important factor in the uptake of aluminum by other tissues, including brain. There have been reports that aluminum is also bound in serum to albumin. While there is evidence for weak binding of aluminum to purified albumin, there is still no convincing evidence that albumin binds a significant amount of aluminum in serum. Administration of the iron chelator desferrioxamine (DFO) results in a sharp increase in ultrafilterable aluminum in serum. This is usually attributed to the formation of the very stable Al-DFO complex. However, some research groups have proposed that the administration of desferrioxamine results in the complexation of aluminum by either an 18 kDa protein named albindin, or by an even smaller 8 kDa protein.