In vitro estimation of the proliferative state of murine bone marrow "colony forming units in culture" (CFUc) with hydroxyurea (HU).

Exposure of CFUc to 1.0 mM of HU for two hours was at the plateau of both the dose--and time--respose curves, killing 38% of the CFUc. This is compatible with the result of the 3HTdR "suicide" method, a standard procedure for the estimation of the proportion of CFUc being in the S phase.