Reutilization of 3H-DNA metabolites by proliferating glial and endothelial cells in the brain of the 14-day-old rat.

The observation of weakly labeled glial and endothelial cells in addition to strongly labeled ones in the brain of the 14-day-old rat from 8 h after 3H-TdR injection on was analysed using autoradiographs with different exposure times. Based on grain density distributions of labeled glial and endothelial cells at different times after 3H-TdR injection and considering cell cycle parameters of these cells it could be shown that the strongly labeled glial and endothelial cells are those which were labeled by the initial 3H-TdR injection. On the contrary the label of the weakly labeled cells, the mean grain density of which is more than 7 times smaller than that of the strongly labeled ones, is obviously due to reutilization of 3H-DNA metabolites.