Application of the critical precipitation assay to complex samples: aluminium binding capacity of human gastrointestinal fluids

摘要

Aluminium is a toxic ion that is partly absorbed from the mammalian gastrointestinal tract. Previous work has noted that the gastrointestinal fluids have their own intrinsic metal binding properties, especially for copper (2+) and iron (3+) ions. To date, however, there have been no investigations with gastrointestinal fluids and the aluminium (3+) ion. Recently we described a critical precipitation assay to examine the binding capacity of single ligands in solution. However, this assay should be applicable to complex solutions of natural systems [i.e., environmental and biological fluids]. Using this technique we now show that human small bowel contents avidly binds aluminium (4.5 mmol L~(-1)) compared to bile (>0.58 mmol L~(-1)) or gastric juice (≥0.17 mmol L~(-1)), while pancreatic juice showed no significant binding (< 0.05 mmol L~(-1)). No significant ~1H NMR detectable ligands were found and from further studies we suggest that soluble mucin may bind aluminium in the gastrointestinal lumen as it does for iron.