Depletion of sodium butyrate from the culture medium of Friend erythroleukemia cells undergoing differentiation.

Friend erythroleukemia cells can be induced to undergo erythroid differentiation by a variety of unrelated compounds. The fact that sodium butyrate causes reversible alterations in growth, morphology, and biochemistry in many cell systems prompted us to reexamine its pattern of induction of differentiation and to compare it to that of dimethyl sulfoxide (DMSO) and hexamethylbisacetamide (HMBA). By the fourth day of induction, a peak in hemoglobin accumulation was reached in the cultures treated with each of these potent inducers. Differences, however, were noted in cultures in which there had been no change of medium for 7 days. Whereas DMSO or HMBA induced cultures reached a stationary stage of growth and maintained a high percentage of benzidine positive cells, butyrate treated cultures resumed active growth and showed a marked decrease in the percentage of benzidine positive cells. However, the actual number of terminally differentiated cells remained relatively constant. The addition of fresh butyrate to 4-day treated cultures prevented the decrease in the percentage of benzidine positive cells. Measurement of [14C]butyrate uptake into the cells showed a decrease in the incorporation of the inducer with time coincident with the decrease in the percentage of benzidine positive cells and of the butyrate in the medium. Incorporation of [3H]thymidine into cells undergoing differentiation for 4 days indicated that butyrate treated cells, but not cells treated with DMSO or HMBA were capable of active DNA synthesis and growth after removal of the inducers. These data suggest that butyrate, a natural fatty acid, is metabolized by the cells and with time its concentration is reduced to a level below that required to stimulate differentiation. Additional evidence to support this notion are the results obtained with conditioned medium (CM) from induced cultures. CM-DMSO and CM-HMBA retained the capacity to induce differentiation whereas CM-butyrate lost its potency with time.