Tumor accumulation of D-selenomethionine-75Se in tumor-bearing mice.

Abstract

The radioactivity distribution of ⁷⁵Se-labeled D-selenomethionine (D-SeMet-⁷⁵Se) was investigated in tumor-bearing mice in order to develop a new radioactive diagnostic agent. D-SeMet-⁷⁵Se was enzymatically prepared from commercially available L-selenomethionine-⁷⁵Se (L-SeMet-⁷⁵Se) by using amino acid reacemase and immobilized L-amino acid oxidase. No difference between D- and L-SeMet-⁷⁵Se was found in the excretion rate into urine and feces in normal mice within 48 h after administration. The in vivo uptake of D-SeMet-⁷⁵Se in both Ehrlich solid tumor and sarcoma- 180 solid tumor was several times higher than that of L-SeMet-⁷⁵Se but the uptake of D- and L-SeMet- ⁷⁵Se were similar in the pancreas. These results indicated that D-SeMet-⁷⁵Se might be useful as a tumor-imaging agent. In vitro experiments on Ehrlich ascites tumor cells showed that D-SeMet-⁷⁵Se was incorporated into the tumor cells by a Na⁺-dependent active transport system similar to L-SeMet-⁷⁵Se and that a transport mechanism specific for D-SeMet-⁷⁵Se might be present in tumor cells in addition to a transport system common to both D- and L-forms.