The effect of 5-bromodeoxyuridine on the postnatal development of the rat cerebellum: a biochemical study

The effect of a thymidine analog, 5-bromodeoxyuridine (BrdU), on the postnatal development of the cerebellum was studied. Rats were injected with 15 mg per 100 gram body weight of BrdU twice a day for 3 consecutive days from the second day after birth, and were killed at 5, 7, 15, 22 and 35 days of age. One hour prior to killing, the rats were given tritiated thymidine. The cerebellar DNA, RNA, protein and cerebroside, and the incorporation of thymidine were measured. BrdU administration caused a markedly retarded growth of the body and the cerebellum. At 35 days of age, the weights of the body and the cerebellum were 42 and 69% of the controls. Quantitative measurements of cerebellar nucleic acids and isotope uptake correlated well with previous morphological observation, and indicated that the analog caused a transient inhibition of cell formation and possibly destruction of stem cell population of the external granular layer. This inhibitory effect was compensated later by a more rapid DNA deposition and a prolongation of the period of cell proliferation. However, the restitution was incomplete and resulted in a permanent deficit in the final cell number, as reflected by the reduction in the size of the cerebellum of the BrdU-treated rats.