Distribution of terbium and increase in calcium concentrations in organs of mice administered with terbium chloride

To investigate the biological effects of terbium (Tb), male mice were intraperitoneally administered with TbCl3 at doses of 10, 50, or 250 mg Tb/kg. The Tb distribution in organs was determined after 18-20 h of injection by using a spectrofluorometer. The concentrations of Ca, Mg, Fe, and Zn in various organs were determined by atomic absorption spectrometer. Tb administered was mainly found in pancreas, seminal vesicles, spleen, liver, and testes. In each organ. Tb concentration increased according to the dosage of Tb. Contrary to our expectation, the increase of Ca concentration was obvious in organs in which high Tb concentrations were found. The correlation coefficients between Tb and Ca concentrations were from 0.863 in spleen to 0.986 in liver. In heart, lung, and blood. Tb was scarcely detected and insignificant change of Ca concentrations was observed. This result suggests that Tb induces increased Ca concentrations in organs.