AL AND SI - THEIR SPECIATION, DISTRIBUTION, AND TOXICITY

Objectives: In dialysis patients both aluminum (Al) and silicon (Si) m ay accumulate. Whereas the toxic effects of Al within this population are clearly established, little is known on the role of Si in the deve lopment/protection of particular dialysis-related diseases. A clear in sight in the protein binding acid speciation of trace elements is impo rtant to better understand the mechanisms underlying their toxicity/es sentiality. Research in this field however is complex and often prone to analytical difficulties and inaccuracies. Design and methods: In th e first part of this review techniques used for speciation studies of Al and Si in biological fluids are discussed. Notwithstanding recent t echnical advances (a) extraneous metal contamination, (b) unrecognized aspecific binding of metals to proteins, and (c) unwanted interaction s with separation equipment such as chromatography columns and ultrafi ltration membranes remain important pitfalls and often lead to erroneo us conclusions. The factors that determine the speciation of Al and Si and their ultimate tissue distribution and toxicity are dealt with in the second part. Here, experimental data obtained with various specia tion techniques are linked to in vivo data on the tissue distribution, localization/toxicity of both elements. Conclusions: A model in which the Al tissue distribution/toxicity is mediated by either its citrate or transferrin bound form is proposed. Copyright (C) 1998 The Canadia n Society of Clinical Chemists.