Activation of JNK by pressure overload is abolished, while that of ERKs and p38-MAPKs is preserved, in MEKK1^–/– mice. Aortic banding (B) or sham operation (S) was performed in MEKK1^+/+ or MEKK1^–/– mice. The animals were sacrificed at 1, 7, or 14 days. (a and b) The kinase activity of p46-JNK was determined by anti–phosphospecific JNK antibody. Duplicate samples were subjected to immunoblot analyses with anti-JNK1 antibody. In b, the mean of the phospho-p46-JNKs/total JNK1 in control mice with sham operation is expressed as 1 in each group. *P < 0.05, **P < 0.001 vs. control sham-operated in each group. (c) Animals were sacrificed at 7 days. The activity of ERKs and p38-MAPKs was evaluated by immunoblotting with anti-phosphospecific antibody. The filters were reprobed with anti–non-phosphospecific antibody after stripping. The results were representative of five samples per group.