Cells (5×106) were treated with arsenite according
to two exposure protocols, subsequently washed twice
with PBS and then supplied with the fresh serum-free
medium for re-incubation, which was the same as the
previously described DNA fragmentation assay except
its duration longer. The cells were harvested nine
times at 4-h intervals for total 32 h after the treatment
beginning, and the progression through cell cycle
was monitored with a DNA flow cytometer. In
brief, trypsinized cells were washed twice with PBS,
fixed with 40% ethanol in PBS at 4 ◦C for 24 h, and
then stained with 5 g/ml propidium iodide (PI) in
PBS containing 50 g/ml RNase A for 30 min. The
DNA content of 10,000 individual cells was analyzed