Translocation and biokinetic behavior of nanoscaled europium oxide particles within 5 days following an acute inhalation in rats
Nanoscaled europium oxide (Eu2O3) particles were inhaled by rats after acute exposure and the potential translocation of particles followed by chemical analysis and transmission electron microscopy (TEM) was investigated. An aqueous dispersion (phosphate buffer/bovine serum albumin) of a commercially available Eu2O3 particle fraction consisting partially of nanoscaled particles was aerosolized with pressurized air. After rapid evaporation, rats inhaled the dry aerosol for 6 h in a single exposure resulting in an alveolar calculated dose of approximately 39.5 mg Eu2O3. Using chemical analysis, 36.8 mg Eu2O3 was detected 1 h after lung inhalation. The amount declined slightly to 34.5 mg after 1 day and 35.0 mg after 5 days. The liver showed an increase of Eu2O3 from 32.3 ng 1 h up to 294 ng 5 days after inhalation. Additionally, lung-associated lymph nodes, thymus, kidneys, heart and testis exhibited an increase of europium over the period investigated. In the blood, the highest amount of europium was found 1 h after treatment whereas feces, urine and mesenteric lymph nodes revealed the highest amount 1 day after treatment. Using TEM analysis, particles could be detected only in lungs, and in the liver, no particles were detectable. In conclusion, the translocation of Eu2O3 within 5 days following inhalation could be determined very precisely by chemical analysis. A translocation of Eu2O3 particulate matter to liver was not detectable by TEM analysis; thus, the overproportional level of 0.8% of the lung load observed in the liver after 5 days suggests a filtering effect of dissolved europium with accumulation.