STUDIES ON THE TRANS-MEMBRANE BEHAVIOR OF RARE-EARTH IONS BY USING FURA-2 AS INDICATOR

Fura - 2 was used to monitor Re3+ ion trans - membrane behavior. The c haracterization of Re3+ - fura - 2 interactions in solutions simulatin g intracellular ionic composition shows that La3+ and Y3+ form 1:1 RE3 + - fura - 2 complexes. As expected, binding of cations devoid of unpa ired electrons (La3+ and Y3+) to fura - 2 is associated with enhanced fluorescence, whereas for cations with unpaired f electrons (Ce3+, Nd3 +, Sm3+, Gd3+, Eu3+, Dy3+, Ho3+, Yb3+) binding to fura - 2 is associat ed with decreased fluorescence. These phenomena were used to measure t he intracellular free RE3+ ions. Mouse myeloma (SP2/0) cells were empl oyed as model cells and exposed to free RE3+ ions or free RE3+ ions wi th some small molecules. The results support the assumption that RE3ions can not enter the cytoplasm of living cells and the experimental small molecules are incapable to improve the permeability of RE3+ ions .