DIFFERENCES IN BEHAVIOR AMONG THE CHLORIDES OF 7 RARE-EARTH ELEMENTS ADMINISTERED INTRAVENOUSLY TO RATS

Differences in behavior among the chlorides of seven pare earth elemen ts (REEs)-yttrium (Y), cerium (Ce), and praseodymium (Pr) (light REEs) ; europium (Eu) and dysprosium (Dy) (medium REEs); ytterbium (Yb) and lutetium (Lu) (heavy REEs)-were investigated through intravenous admin istration of the REEs to rats. (1) Distributions of REEs and mineral c oncentrations in the organs on Day 1 were investigated at low and high doses (9-10 and 18-20 mg REE/kg, or 56-66 and 112-132 mu mol REE/kg). More than 78% of the REEs administered was distributed into liver, bo ne, and spleen. High doses of Y, Eu, and Dy markedly increased the acc umulation of REEs in spleen and lungs as well as the concentration of Ca in liver, spleen, and lungs. (2) The distribution patterns of REEs and changes in Ca concentrations in major organs over time were invest igated by the administration of Pr, Eu, Dy, Yb (low dose), and Y (high dose). REEs disappeared from the blood within 1 day but were retained in the organs for a long time. The percentages of the doses of Y, Eu, Dy, and Yb found in the liver were highest at 8 hr to 2 days, then de creased gradually; hepatic Pr levels, however, remained high. Changes in Ca concentrations in liver, spleen, and lungs were in accordance wi th those of REEs. (3) Severe hepatotoxicity was observed after adminis tration of Ce and Pr; fatty liver, jaundice, and elevated serum GOT an d GPT levels were most prominent on Day 3. Therefore, we hypothesized that REE chlorides might be categorized into three groups according to their ionic radii (light REEs, Y and medium REEs, and heavy REEs) and from their behavior, i.e., distribution pattern, Ca-accumulating acti on, and hepatotoxicity. (C) 1997 Society of Toxicology.