Cytogenetic assays for mitotic poisons: the diploid Chinese hamster cell system

When the diploid Chinese hamster cells (line Don) were treated with Colcemid (final concentrations 0.05 micrograms/ml and 2 mg/ml) for three hours and the mitotic arrest was reversed by washing and reincubation in the control medium, the cells were able to reorganize spindle and divide within 2-4 hr. When the cells were treated with vinblastine (concentrations 10(-6) and 10(-4) M), there was a continuous accumulation of mitoses after vinblastine was removed. At 10(-6) M, a small proportion of anaphase figures was observed in reversed cell populations but at 10(-4) M, there was no anaphase. The results suggest that tubulin was precipitated or destroyed even in cells in interphase. The G2 and S cells were able to complete their cell cycle but were unable to divide because of the lack of microtubules. When recovery was prolonged to 24, 48 and 72 hr, the cell populations exhibited higher percentages of polyploid and aneuploid elements than the control cell populations. There appeared to be a nonrandom increase of the small metacentric than the larger chromosomes. This test system, after protocol improvements, should be useful to assay mitotic poisons that are water soluble or soluble in DMSO.