(A) HKM were transfected with PKACA-siRNA, scrambled siRNA or pre-treated with H-89, U 0126 then infected with A. hydrophila and checked for total ERK and pERK activity 24 h p.i. using EIA based kits. HKM were pre-treated with or without U 0126 then infected with A. hydrophila and checked for (B) Hoechst 33342 positive cells and caspase-3 activity and (C) AV-PI staining 24 h p.i. Vertical bars represent mean ± SE (n = 6). *P<0.05, compared to HKM; γP<0.05, compared to HKM+Sc; #P<0.05, compared to HKM+B; ±P<0.05, compared to HKM+Sc+B. HKM, control head kidney macrophage; HKM+Sc, HKM transfected with scrambled siRNA; HKM+B, HKM infected with A. hydrophila; HKM+Sc+B, HKM transfected with scrambled siRNA infected with A. hydrophila; HKM+PKACA-siRNA+B, HKM transfected with PKACA-siRNA infected with A. hydrophila; HKM+H-89+B, HKM pre-treated with H-89 infected with A. hydrophila; HKM+U 0126+B, HKM pre-treated with U 0126 infected with A. hydrophila.