For that HKM were pre-treated with or without U 0126 prior to infection with A. hydrophila and checked for apoptotic death using Hoechst 33342, AV-PI staining and caspase-3 activity 24 h p.i. It is clear from Figure 5B and 5C that inhibition of ERK 1/2 significantly inhibited (P<0.05) A. hydrophila-induced HKM apoptosis and lowered caspase-3 activity. The gene discussed is CASP3; the disease is infection.