Effect of cadmium on the relationship between replicative and repair DNA synthesis in synchronized CHO cells

Repair and replicative DNA synthesis were measured at different stages of the cell cycle in control and cadmium-treated Chinese hamster ovary (CHO-K1) cells. Cells were synchronized by counterflow centrifugal elutriation. Elutriation resulted in five repair and four replication subphases. On Cd treatment, repair synthesis was elevated in certain subphases. Replicative subphases were suppressed by Cd treatment, with some of the peaks almost invisible. The number of spontaneous strand breaks measured by random oligonucleotide primed synthesis assay showed a cell-cycle-dependent fluctuation in control cells and was greatly increased after Cd treatment throughout the S phase. Elevated levels of the oxidative DNA damage product, 8-oxodeoxyguanosine, were observed after Cd treatment, with the highest level in early S phase, which gradually declined as damaged cells progressed through the cell cycle.