Strong inhibition of replicative DNA synthesis in the developing rat cerebral cortex and glioma cells by roscovitine

The effects of the cyclin-dependent kinase inhibitors roscovitine and olomoucine on DNA synthesis rate during normal rat brain development were studied by using short time (90 min) incubation. Both purine analogues at 100 μM concentration decreased the DNA synthesis of rat cerebral cortex in an age-dependent manner. The maximun inhibitory effect (~ 90% for roscovitine, ~ 60% for olomoucine) occurred in rats of 2–13 days postnatal age. In adult rats (> 60 days postnatal age), the effect of both purine analogues was low. Roscovitine even at 200 μM concentration did not inhibit the fraction of DNA synthesis insensitive to hydroxyurea (unscheduled DNA synthesis (UDS)). In addition, in the RG2 rat glioma model, roscovitine produced a strong inhibition of DNA synthesis in glioma cells when compared to adult normal tissue. Since in adult rat brain more than 60% of DNA synthesis is related to DNA repair, usually measured as UDS, our results indicate that roscovitine strongly blocks ongoing DNA synthesis connected with replicative processes.