We have found that cultured differentiated astrocytes pretreated with N⁶, 2^'-O-dibutyryladenosine 3',5'-cyclic monophosphate (DBcAMP), a permeable analogue of cAMP, incorporate thymidine, but not uridine, via nucleoside transporters into TCA insoluble fraction for repair on DNA injury in the presence of hydrogen peroxide (H₂O₂) at an early time, and these phenomena are specific in differentiated astrocytes, but not undifferentiated astrocytes and neurons.
We studied expression of nucleoside transporters in cultured astrocytes by RT-PCR, western blot analysis and immunocytochemistry. We could confirm CNT2, that is pyrimidine selective nucleoside transporter, CNT3, that is non-selective nucleoside transporter, ENT1, that is hypersensitive nucleoside transporter, and ENT2, that is low-sensitive nucleoside transporter, but not CNT1, that is purine selective nucleoside transporter and confirmed non-presence in brain, in cultured astrocytes.
These results indicate that H₂O₂-induced thymidine incorporation could pass through specific nucleoside transporters, existed in cultured astrocytes.