Lithium inhibits terminal differentiation of erythroleukemia cells. Evidence for a pre-commitment 'priming' event

Lithium has been found to be a novel inhibitor of the terminal differentiation of Friend murine erythroleukemia cells. A general method for the quantitative analysis of differentiation inhibitors has been developed and used to compare the site of inhibition by lithium with that by vanadate. Lithium inhibits the commitment to differentiation (K 1/2 approximately 10 mM) induced by DMSO (dimethylsulfoxide) at non-toxic concentrations that have only a small effect on the rate of proliferation. Inhibition is reversible and probably requires entry of Li+ into the cell, since it is blocked by high KCl in the medium. LiCl is most effective when present during the first 10 h of DMSO treatment, before commitment is initiated. Computer-assisted analysis of the kinetics of commitment demonstrate that inhibition by lithium is best described by including a lithium-sensitive 'priming' event, which occurs with high probability prior to commitment.