(A) Cell lysates of HKM infected with A. hydrophila were checked for intracellular cAMP release at indicated time point p.i. using EIA kit. (B) HKM pre-treated with KN-93 or KN-92 were infected with A. hydrophila and cAMP release was measured in the cell lysates at 24 h p.i. (C) HKM were transfected with CaMKIIg-siRNA, PKACA-siRNA or scrambled siRNA or pre-treated with KN-93 or H-89 then infected with A. hydrophila and PKACA activation and nuclear translocation checked by immunofluorescence. The images are representative of three independent experiments. Vertical bars represent mean ± SE (n = 6). *P<0.05, compared to HKM; #P<0.05, compared to HKM+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+CaMKIIg-siRNA+B, HKM transfected with CaMKIIg-siRNA infected with A. hydrophila; HKM+PKACA-siRNA+B, HKM transfected with PKACA-siRNA infected with A. hydrophila; HKM+KN-93+B, HKM pre-treated with KN-93 infected with A. hydrophila; HKM+KN-92+B, HKM pre-treated with KN-92 infected with A. hydrophila; HKM+H-89+B, HKM pre-treated with H-89 infected with A. hydrophila.