Abstract
The purpose of this study is to evaluate 14C-thymidine as a tracer, to detect radiation damages in gut.
In unirradiated mice, 14C-thymidine accumulated in gut within 30 min after an intravenous injection and reached a plateau. The plateaued accumulation of 14C-thymidine in gut was 18-folds higher than that in plasma.
We examined the thymidine accumulation in irradiated gut. Mice were given whole body irradiation with carbon-ion (290MeV/u, 6cm-SOBP, 20keV/µm). Accumulation in gut of 2-[14C]-thymidine decreased with an increase of carbon-ion doses (1-9 Gy), whereas that of 6-[3H]-thymidine was independent of radiation dose. These results suggest that the difference of isotope-labeled position causes change of thymidine kinetics. In addition, we investigated blood flow in gut using 14C-IMP. The blood flow decreased by 25 % after 1 Gy irradiation or over, suggesting that blood flow should be taken account for the evaluation by 14C-thymidine.
Furthermore, to evaluate the radioprotection, mice were pretreated with bFGF and MK801. Radioprotectors of bFGF and MK801 increased DNA synthesis in gut by a factor of 1.5 at 84 hours after carbon-ion (9 Gy) irradiation while number of crypts was not affected by radioprotectors. These findings demonstrated that the thymidine uptake in vivo could be an appropriate marker for investigating gut responses and radioprotection.
