Phases of the cell cycle sensitive to endoreduplication induction in CHO-K1 cells.

We investigated the sensitive phase of the cell cycle for endoreduplication induction by colchicine, vanadate, 4-nitroquinoline 1-oxide (4NQO), and hydrazine in Chinese hamster CHO-K1 cells, compared to the metaphase endoreduplication inducer rotenone. Treatment of asynchronous cultures and 5-bromodeoxyuridine (BrdU) labeling analysis showed that the detected endoreduplications originated from cells which had been treated with these inducers in S, G2, or metaphase. Exposure to synchronized metaphase cells revealed that the inducers did not lead metaphase cells to endoreduplicate. These results were markedly different from that of rotenone and suggested that the target for the induction of endoreduplication by the tested compounds existed between at least S and G2 phases.