THE EFFECTS OF DIAZEPAM ON MITOSIS AND THE MICROTUBULE CYTOSKELETON .2. OBSERVATIONS ON NEWT EPITHELIAL AND PTK1 CELLS

The effects of diazepam (DZP) on mitosis and the microtubule (MT) cyto skeleton were examined using live and fixed PtK1 and newt (Taricha gra nulosa) epithelial lung cells. DZP treatment caused rapid shortening o f spindle MTs at prometaphase and metaphase inducing movement of the p oles together while chromosome oscillations continued. DZP treatment s lowed the rate of anaphase A bur did not detectably affect anaphase B, cell cleavage or interphase cells. Our results suggest that DZP inhib its mitosis by affecting prometaphase and metaphase MTs. its action is not equivalent to that of common anti-MT drugs, since only a small su bpopulation of MTs are significantly susceptible. Likewise, its effect s are not equivalent to those generated by metabolic inhibitors. The r elated benzodiazepines, madazepam and oxazepam, induce effects equival ent to those of DZP.