Distribution of some rare earth elements and their binding species with proteins in human liver studied by instrumental neutron activation analysis combined with biochemical techniques

Distribution patterns of three rare earth elements and their binding species with proteins in the human liver samples were studied by instrumental neutron activation analysis combined with biochemical techniques. It was indicated that La, Ce and Sm were highly concentrated in microsomes, although the total content of this fraction was the least among all of the liver organelles, which was similar with the behavior of Ca and Fe. More than 85% of La, Ce and Sm was present in the cytosolic protein fractions separated by ammonium sulfate and ethanol. It indicated that these elements were mainly incorporated into protein. It was also revealed by means of size-exclusion chromatography that at least three La-binding proteins (Mw: 335±50, 94.5±15.4, 13.6±3.8kD), three Ce-binding proteins (Mw: 335±50, 85.1±12.0, 22.8±6.3kD) and about four Sm-binding proteins (Mw: 335±70, 82.1±5.4, 32.3±5.8 and 13.6±4.5kD) were present in the supernatant fraction of human liver. Most of La, Ce and Sm were found in the high-molecular-weight protein region.