Effect of 8-hydroxy-, 8-mercapto- and 5-chloro-7-iodo-8-hydroxy-quinoline on the uptake and distribution of nickel in mice.

Oral administration of Ni2+ together with 8-hydroxyquinoline (8-OH-quinoline), 8-mercaptoquinoline (8-SH-quinoline) or 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol) resulted in increased tissue levels of the metal in several tissues of mice in comparison with animals given the Ni2+ alone. Ni2+ forms lipophilic complexes with these compounds and it can be assumed that this will facilitate the uptake of the Ni2+ over the walls of the gastrointestinal tract. Our results showed that 8-SH-quinoline, in contrast to 8-OH-quinoline and and clioquinol, induces a markedly changed distribution pattern of the Ni2+ in the body, with uptake of the metal in tissues such as the central nervous system, pigmented tissues, the pancreatic islets and the thyroid. It is probable that the Ni(2+)-complex with 8-SH-quinoline is stable enough to persist for a time period in the tissues and that the obtained pattern partly reflects the distribution of the complexed metal. In contrast, following the absorption from the gastrointestinal tract there may be a dissociation of the complexes between Ni2+ and 8-OH-quinoline or clioquinol, resulting in increased metal levels in various tissues, but with similar distribution as when the Ni2+ is given alone.