Studies on the Biological Effects of Rare Earth Elements. III. Fate of Chlorides of Dy, Eu, Yb and Y in the Rat after Intravenous Administration.

Abstract

Four kinds of rare earth element solutions [(10mg/kg as rare earth elements), i. e. dysprosium chloride (DyCl3), europium chloride (EuCl3), ytterbium chloride (YbCl3) and yttrium chloride (YCl3)], were administered intravenously from the caudal vein of rat. The excretion into the feces and urine, and the concentration and the distribution (% of dose) of rare earth elements in the whole blood, liver, kidney, lung, spleen and bone were investigated as a function of time. The results were as follows : 1) The administered rare earth elements were excreted gradually into the feces for 7d. The excretion rate accounts for 5.4-18.4%. The excretion of Y was lower than the other 3 kinds of rare earth elements. No rare earth elements were detected from the urine. 2) Rare earth elements in the whole blood disappeared within 1d. Y in the whole blood disappeared within 4h after the administration. 3) The major organs for accumulation of the administered rare earth elements were liver, spleen and bone. The distribution (% of dose) of rare earth elements in the liver was the highest level at 8h to 2d after the administration, then decreased gradually. The levels of distribution of rare earth elements in the kidney and lung were low during the experimental period. The distributions of Dy, Eu and Yb in these organs increased till 1d after the administration, and then almost unchanged. On the contrary, the distribution of Y in the spleen was larger than those of Dy, Eu and Yb, and increased as a function of time during the experimental period. The distribution of rare earth elements in bone increased gradually as a function of time. The highest level was observed in the case of Yb administration. Therefore, it was suggested that the rare earth elements in the blood disappeared within 1d, and that the rare earth elements were accumulated mainly in the liver, spleen and bone and retained for a long time.