Effects of cyclic AMP on the growth of differentiating and undifferentiated friend erythroleukemic cells

Elevated concentrations of cyclic AMP elicit only minor reductions in growth rate and saturation density in undifferentiated Friend erythroleukemic cells. During the course of dimethylsulfoxide (DMSO)‐induced differentiation, Friend cells convert from a cyclic AMP‐tolerant state to a phenotype characterized by a high degree of sensitivity to cyclic AMP‐mediated growth arrest. Conversion to cyclic AMP sensitivity is detectable after 30 hours growth in medium containing 2% DMSO, and either 0.5 mM 8‐Br‐cyclic AMP or 5 nM cholera toxin. Cultures of differentiating Friend cells achieved a stationary phase density that was approximately 8‐fold higher than the cell density observed in parallel, differentiating cultures treated with 0.5 mM 8‐Br‐cyclic AMP. Temporally, the appearance of cyclic AMP‐sensitivity corresponds to the early expression of in vitro erythroid differentiation (Ross et al., ′74), but growth arrest does not alter the subsequent accumulation of hemoglobin in non‐dividing DMSO‐induced cells. Since growth arrest is preceded by a round of cell division, these observations are consistent with the concept that DMSO must be present during DNA replication for the subsequent expression of hemoglobin synthesis (McClintock and Papaconstantinou, ′74; Levy et al., ′75; Harrison, ′76).