l-tyrosine ([125I]IMT) uptake to radiotherapy of C10 glioma cells was compared to elucidate the intracellular reactions that affect the response of 2-amino-4-([11C]methylthio)butyric acid ([11C]Met) uptake to radiotherapy.Methods
After irradiation of cultured (3 Gy) or xenografted C10 glioma cells (25 Gy) using a carbon ion beam, the accumulation of [14C]Met and [125I]IMT in the tumors was investigated. The radiometabolites in xenografted tumors after radiotherapy were analyzed by size-exclusion HPLC.
Results
[14C]Met provided earlier responses to the carbon ion beam irradiation than [125I]IMT in both cultured and xenografted tumors. While [125I]IMT remained intact in xenografted tumor before and after irradiation, the radioactivity derived from [14C]Met was observed both in high molecular fractions and intact fractions, and the former decreased after irradiation.
Conclusion
The earlier response of [11C]Met uptake to tumor radiotherapy could be attributable to the decline in the intracellular energy-dependent reactions of tumors due to radiotherapy.
