Figure 4.

Hyperosmolarity induces p38 and p42/44 activation in HT-29 cells (A). Cells were incubated with hyperosmotic medium prepared by the addition of mannitol (for a final concentration of 100 mmol/L) to isosmolar medium for the indicated time periods. p38 and p42/44 activation was determined using Western blotting using antibodies raised against the active, double-phosphorylated form of p38 and p42/44. This figure is representative of two separate experiments. Treatment of HT-29 cells with the selective p38 inhibitor SB203580 or selective p42/44 inhibitor PD98059 suppresses the hyperosmolarity-induced IL-8 response (B). Hyperosmolarity was achieved by the addition of mannitol (for a final concentration of 100 mmol/L) to isosmolar medium. In control wells, cells were incubated with isosmolar medium. Data are mean ± SEM of n = 12 wells from two separate experiments. *, P < 0.05; **, P < 0.01. Dotted bar, no mannitol; cross-hatched bars, mannitol.