Fig. 4. Time course of p38-MAPK phosphorylation in the amphibian heart, in response to reperfusion after CuCl₂ treatment. (A) Phospho-p38-MAPK was detected in extracts (50 µg protein) from control hearts (Con), hearts perfused with 500 µmol l^–1 CuCl₂ for 15 min or hearts perfused for the indicated times with normal bicarbonate-buffered saline following the 15 min perfusion with 500 µmol l^–1 CuCl₂. As a positive control, extract from hearts perfused with 50 µmol l^–1 H₂O₂ for 2 min was used (Ai). Equal loading was assessed, as previously, using an actin antibody (Aii). (B) Densitometric analysis of phospho-p38-MAPK bands by laser scanning. Results are means ± s.e.m. for three independent experiments. Re, reperfusion. ^*P<0.05, ^**P<0.01, P<0.001 vs control value.