Fig. 5. Effect of the selective inhibitor SB203580 on the p38-MAPK phosphorylation induced by oxidative stress. Protein (100 µg) from hearts perfused with 100 µmol l^-1 H₂O₂ for 2 min in the absence or presence of 1 µmol l^-1 SB203580 was assessed by immunoblot using phosphospecific anti-p38-MAPK (A, top panel) or total anti-p38-MAPK antibody (A, bottom panel). As a positive control, extract from hearts perfused with 0.5 mol l^-1 sorbitol was included. Blots are representative of three independent experiments. (B) Densitometric analysis of phospho-p38-MAPK bands by laser scanning. Results are means ± S.E.M. for three independent experiments. P<0.001 vs control value.