Differential effects of external agents on the G1-S transit rate of murine pluripotent hemopoietic stem cells (CFUs) after their release from G0.

The divalent ionophore A-23187, isoproterenol or testosterone are known among several agents to switch the pool of G0 murine femoral CFUs back into the cell cycle. The short transit time of these stem cells between late G1 and the S phase was further reduced by a factor of two after treatment with the divalent ionophore as compared with the other two agents. Interference of actinomycin D with such processes that immediately follow the release of the blocked CFUs suggested possible differences related to the type of agent used in the steps that control the progress of these cells out of late G1 into the replicative phase.