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

INTRODUCTION
and antiperspirants containing aluminium chlorohydrate (Flarend et al. 2001) represent
other possible sources of exposure.
Aluminium toxicokinetics
Absorption of aluminium
Aluminium may be absorbed by several routes: oral, intranasal, transdermal, and
parenteral pathways. The major sites of aluminium absorption are the gastrointestinal
tract (Ittel 1993), the skin (Exley 1998, 2004), and the olfactory and oral epithelia
(Roberts 1986).
Oral absorption
The gastrointestinal tract is one of the main sites of aluminium absorption (Ittel
1993). The proportion of absorbed aluminium following oral intake is very low ranging
from 0.06 to 1.5% (Moore et al. 2000, Flaten et al. 2001, Yokel et al. 2001a). The
amount of aluminium absorbed across the gastrointestinal tract depends on many
factors, including pH, aluminium speciation and dietary agents (Partridge et al. 1989,
Deng et al. 1998). Moreover, the intestinal absorption of aluminium was shown to
increase in various pathological conditions, such as AD (Moore et al. 2000). As an
example, a low pH will enhance the solubility of aluminium species then increasing
aluminium absorption. Small organic acids also present in the diet of man, including
citrate, lactate, and ascorbic, gluconic, malic, oxalic, and tartaric acids, are able to
prevent its precipitation during transit as they complex with the metal, increasing its
absorption from the gastrointestinal tract (Deng et al. 2000, Venturini-Soriano and
Berthon 2001, Whitehead et al. 1997), and to aument tissue retention of aluminium in
rats orally dosed with aluminium (Domingo et al. 1991, 1994). On the other hand
phosphorus, silicone and other dietary factors such as phytate and polyphenols seem to
decrease absorption (Yokel and O‟Callaghan 1998, Powell and Thompson 1993, Powell
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