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Silicon in natural waters and the bioavailability of aluminium
ENVIRONMENTAL/TRACE
METAL CHEMISTRY
347
N()w
SILICON IN NATURAL WATERS AND THE BIOAVAILABILITY OF ALUMINIUM. J. D. Birchall, J. S. Chappell, Imperial Chemical Industries Plc, P. 0. Box 11, The Heath, Runcom, Cheshire, WA7 4QE, U.K. C. Exley, Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, U.K. We recently reported [l] the elimination of the acute toxicity to fish from aluminium in acid waters by the presence of dissolved silicon (silicic acid). This effect results from the stable formation of hydroxy-aluminosilicate species, which blocks the tight binding of aluminium to gill structures and inhibits the absorption of aluminium into body tissues. This chemistry suggests that the naturally occurring levels of silicon in environmental waters can be instrumental in limiting the bioavailability of aluminium to aquatic life. Similarly, these levels of silicic acid in the diet (via drinking water) for higher animals may be an environmental factor restricting aluminium absorption in the gut. [l] J. D. Birchall, et al., Nature, 1989,338, 146.
COMPLEXES IN NO10 ALUMINUM(III) SYSTEMS: FACT AND FICTION.
BIOLOGICAL AND ENVIRONMENTAL A. E. Martell and R. J. Motekaitis, College Station, TX 77843-3255, USA. Texas A.&M University, Because AI(II1) has strong tendencies toward hydrolysis and formation metastable polynuclear hydroxo complexes, many of the of long-lasting published papers on AI(II1) complexes are either incorrect or of doubtful validity [l]. Examples of well-established complex species will be described. Desferriferrioxamine B (DFB), which is proposed for the treatment of Al(II1) overload diseases, dominates AI(III) complexation in competition with other except at very high pH where polyphenols ligands over a wide pH range, such as catechol are more effective. [l] A. E. Martell and R. J. Motekaitis, in “The Environmental Chemistry and Toxicology of Aluminum”, T. E. Lewis, Ed., Lewis Publishers, Chelsea, MI,in press.
NOll
ALUMINIUM CHELATION WITH DESFF.RKIOKAMINE. J.P.Day and P.Ackrill Department of Chemistry, University of Manchester, Ml.3 9PL, and University Hospital of South Manchester, Withington, PI20 8I.K. U.K. Aluminium intoxication, in renal patients and others, causes at least 3 serious/fatal conditions: encephalopathy, a bone disease and a microcytic anaemia. These are treated effectively by desferrioxamine (DFO) chelation, introduced in 1979 [l]. We report on the in vivo chemistry of DFO chelation, studied in 70 patients over 10 years, particularly the removal of Al from competitive binding sites and interactions with other metals. DFO releases Al and Fe from bone phosphate, liver ferritin, and red cell ceruloplasain, but not from transferrin binding in plasma. The parallel kinetics of Fe and Al release from liver by DFO suggests similarity of binding site. [l] P.Ackrill, J-P-Day, et al., m, ii, 692 (1980).
METAL CHEMISTRY
347
N()w
SILICON IN NATURAL WATERS AND THE BIOAVAILABILITY OF ALUMINIUM. J. D. Birchall, J. S. Chappell, Imperial Chemical Industries Plc, P. 0. Box 11, The Heath, Runcom, Cheshire, WA7 4QE, U.K. C. Exley, Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, U.K. We recently reported [l] the elimination of the acute toxicity to fish from aluminium in acid waters by the presence of dissolved silicon (silicic acid). This effect results from the stable formation of hydroxy-aluminosilicate species, which blocks the tight binding of aluminium to gill structures and inhibits the absorption of aluminium into body tissues. This chemistry suggests that the naturally occurring levels of silicon in environmental waters can be instrumental in limiting the bioavailability of aluminium to aquatic life. Similarly, these levels of silicic acid in the diet (via drinking water) for higher animals may be an environmental factor restricting aluminium absorption in the gut. [l] J. D. Birchall, et al., Nature, 1989,338, 146.
COMPLEXES IN NO10 ALUMINUM(III) SYSTEMS: FACT AND FICTION.
BIOLOGICAL AND ENVIRONMENTAL A. E. Martell and R. J. Motekaitis, College Station, TX 77843-3255, USA. Texas A.&M University, Because AI(II1) has strong tendencies toward hydrolysis and formation metastable polynuclear hydroxo complexes, many of the of long-lasting published papers on AI(II1) complexes are either incorrect or of doubtful validity [l]. Examples of well-established complex species will be described. Desferriferrioxamine B (DFB), which is proposed for the treatment of Al(II1) overload diseases, dominates AI(III) complexation in competition with other except at very high pH where polyphenols ligands over a wide pH range, such as catechol are more effective. [l] A. E. Martell and R. J. Motekaitis, in “The Environmental Chemistry and Toxicology of Aluminum”, T. E. Lewis, Ed., Lewis Publishers, Chelsea, MI,in press.
NOll
ALUMINIUM CHELATION WITH DESFF.RKIOKAMINE. J.P.Day and P.Ackrill Department of Chemistry, University of Manchester, Ml.3 9PL, and University Hospital of South Manchester, Withington, PI20 8I.K. U.K. Aluminium intoxication, in renal patients and others, causes at least 3 serious/fatal conditions: encephalopathy, a bone disease and a microcytic anaemia. These are treated effectively by desferrioxamine (DFO) chelation, introduced in 1979 [l]. We report on the in vivo chemistry of DFO chelation, studied in 70 patients over 10 years, particularly the removal of Al from competitive binding sites and interactions with other metals. DFO releases Al and Fe from bone phosphate, liver ferritin, and red cell ceruloplasain, but not from transferrin binding in plasma. The parallel kinetics of Fe and Al release from liver by DFO suggests similarity of binding site. [l] P.Ackrill, J-P-Day, et al., m, ii, 692 (1980).