Fig. 5.

Effects of inhibition of p38α on proliferation and apoptosis of primary erythroid progenitors. (A) Erythroid progenitors cultured in serum-containing media with Epo and SCF were treated with SB203580 inhibitor 24 h before harvesting the cells for proliferation assays. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was performed on days indicated along with control samples that were not treated with the inhibitor. The data are means ± SE of triplicate measurements. (B) Erythroid progenitors on day 8 were washed to eliminate growth factors (Epo and SCF) and were recultured with the SB203580 inhibitor and growth factors or without the inhibitor treatment but with growth factors. Also, two samples were recultured without growth factors as indicated. After 20 h, cells were harvested and the percentage of apoptotic cells in each sample was determined by flow cytometry using annexin V and propidium iodide as apoptotic markers.