ERK1/2 and Akt but not p38 MAPK are involved in linoleic acid-induced upregulation of COX-2. Endothelial cells were pretreated with or without the Akt inhibitor LY294002 (LY, 10 μM for 1 h), the p38 MAPK inhibitor SB 203580 (SB, 10 μM for 1 h) or the ERK1/2 inhibitor PD98059 (PD, 20μM for 1 h), followed by exposure to linoleic acid (LA, 90 μM) for 6 h. Activation of COX-2 was determined by western blot analysis (Figure 5). The western blot shown represents one of three experiments. Densitometry results shown in parallel represent mean ± SEM of three independent experiments. *Significantly different compared to control cultures. #Significantly different compared to cultures treated only with linoleic acid.