Biliary excretion of nickel in rats

Nickel (Ni) concentrations were determined by liquid scintillation spectrometry or electrothermal atomic absorption spectrophotometry in bile and plasma samples obtained from male rats following subcutaneous (s.c.) injection of 63NiCl2 (1.7 mumol/kg) or non-radioactive NiCl2 (125 or 250 mumol/kg). During the intervals from 1-6 or 11-16 h post-injection, the bile:plasma ratios of Ni concentrations ranged from 0.045-0.13, and the excretory clearance of Ni in bile ranged from 0.027-0.055 ml/h. The estimated biliary excretion of Ni in the 24 h post-injection amounted to less than 0.5% of the respective doses of NiCl2. Contrary to previous findings with other divalent metal ions, this study shows that biliary excretion is quantitatively unimportant for the elimination of exogenous Ni(II) in rats.