Aluminium toxicity and metal speciation: Established data and open questions

Histopathological findings in humans and extensive toxicological investigation in vivo and in vitro point to an unambiguous neurotoxic potency of Al(III). Experimental toxicology with aqueous Al(III) is very difficult owing to the complex and somewhat uncontrollable aqueous chemistry of the metal centre in the neutral range. The choice of neutral, hydrolytically stable synthetic toxins makes possible both the control of metal speciation and of analytical metal concentration down to about 1 mM in neutral buffered solutions. The employment of less stable complexes like Al-2(citrate)(2)(H2O)(6) and Al(lactate)(3) or of ordinary salts is unavoidably complicated by the precipitation of Al(OH)(3) under the same conditions. In spite of this, the choice of a carefully designed protocol, based on ensuring well defined steps, enables one to successfully control the analytical metal concentration down to 10 mu M Al(III). The control of the metal speciation at these concentration levels remains an open question.