Role of FeCl3 in 67Ga uptake by HeLa S3 cells in vitro.

The effect of FeCl3 on 67Ga uptake by HeLa S3 cells was studied in vitro. Uptake of 67Ga by HeLa S3 cells was influenced by the concentrations of serum in the medium and especially that of transferrin added to the medium. Therefore, it is assumed that a mechanism of 67Ga uptake exists mediated by transferrin. However, when 10(-2)--10(-1) mM FeCl3 was added to the medium in the same experimental system, a remarkable increase of 67Ga uptake was noted. Results of equilibrium dialysis, showed that binding of 67Ga to transferrin was inhibited by the administration of FeCl3. Moreover, the formation of a complex of 67Ga and FeCl3, which did not pass through the cellulose membrane, was observed. A correlation was found between an increase in 67Ga uptake by HeLa S3 cells and the formation of the 67Ga--Fe complex. These results indicate that another mechanism of 67Ga accumulation, namely the formation of a 67Ga--Fe complex plays a role in the uptake of 67Ga by tumor cells in the presence of iron.