Effect of ERK inhibitor UO126 and p38 inhibitor SB203580 on butyrate-mediated erythroid differentiation of K562s cells.

Cells were cultured for 4 days in the absence (white bars) or presence (black bars) of butyrate. Simultaneous addition of both inhibitors are shown as dashed bars (A and B: 10 μM SB203580 plus increasing concentrations of UO126) or dotted bars (C and D: 10 μM UO126 plus increasing concentrations of SB203580). Inhibitors were added 1 hour prior to butyrate. Cell numbers were counted and cells were then harvested and lysed. Hemoglobin and protein concentrations were determined as described in “Materials and methods.” Each experiment was performed 4 times and standard errors were calculated as indicated.