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 t he cell cycle in control and cadmium-treated Chinese hamster ovary (CHO-K1) cells. Cells were synchronized by counterflow centrifugal elutriation. Elu triation resulted in five repair and four replication subphases. On Cd trea tment, repair synthesis was elevated in certain subphases. Replicative subp hases were suppressed by Cd treatment, with some of the peaks almost invisi ble. The number of spontaneous strand breaks measured by random oligonucleo tide primed synthesis assay showed a cell-cycle-dependent fluctuation in co ntrol cells and was greatly increased after Cd treatment throughout the S p hase. Elevated levels of the oxidative DNA damage product, 8-oxodeoxyguanos ine, were observed after Cd treatment, with the highest level in early S ph ase, which gradually declined as damaged cells progressed through the cell cycle.