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 specific nucleoside transporters, ENT2 and CNT3, 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. Purine and pyrimidine nucleosides are DNA and RNA precursors consisting of base and ribose.
We studied the influence of purine and pyrimidine nucleosides on H₂O₂-induced thymidine incorporation into cultured astrocytes. Adenosine and guanosine, RNA precursor purine nucleosides, decreased H₂O₂-induced thymidine incorporation. On the other hand, Deoxyadnosine and deoxyguanosine, DNA precursor purine nucleosides, increased it. Cytidine, RNA precursor pyrimidine nucleoside, did not influence it, but deoxycitidine, DNA precursor pyrimidine nucleoside, decreased it.
These results indicate that H₂O₂-induced thymidine incorporation into cultured astrocytes are increased synergistically by purine nucleosides, but not pyrimidine nucleosides.