Mechanisms of aluminium neurotoxicity in oxidative stress-induced ...

INTRODUCTION
Coble 1987). Transdermal absorption of only 0.012% has been reported after a one-time
underarm application of 26 Al chlorhydrate (Flarend et al. 2001) while a case report
showed that transdermal uptake of aluminium may also be important (Guillard et al.
2004).
Distribution of aluminium in the body
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Once absorbed into the bloodstream, aluminium circulates bound to various
plasma proteins: 93% is bound to transferrin, 6% to citrate and the remaining to
hydroxide and phosphate (Harris et al. 2003). The metal is distributed unequally to all
tissues within the body throughout normal and aluminium-intoxicated individuals
(Alfrey et al. 1980, Di Paolo et al. 1997), and aluminium-treated experimental animals
(Greger and Sutherland 1997). The highest levels of aluminium in mammalian tissues
are found in the skeleton and lungs, approximately 50% and 25% of the 30 to 50 mg
aluminium body burden in the healthy human subject (Alfrey 1984, Ganrot 1986,
ATSDR 1999). Aluminium also accumulates in human brain, skin, lower
gastrointestinal tract, lymph nodes, adrenals, and parathyroid glands (Tipton and Cook
1963, Hamilton et al. 1973, Cann et al. 1979, Alfrey 1980).
Aluminium accumulation in different target organs varies with the aluminium
salt administered, species studied and route used, dose and duration of exposure (Ding
and Zhu 1997, Yokel and McNamara 1988), but also with age, kidney function, disease
status, and dietary compounds (Greger 1993). The human brain contains lower levels of
aluminium when compared to other organs (Walker et al. 1994, Andrási et al. 2005,
Yokel and McNamara 2001). In the case of dialysis encephalopathy, this concentration
may aument drastically (Alfrey et al. 1976).