Effect of the phosphodiesterase (PDE) inhibitor IBMX on the cAMP response to EPA. A: EPA-induced cAMP response as measured using EpacH90 was eliminated in NCM460 cells after exposure to ionomycin and IBMX. B: EpacH30 response to 50 μM EPA in the presence of the PDE inhibitor IBMX (2 mM) and response to IBMX in the presence of EPA in the same NCM460 cell. C: summary of data expressed as line scatter plots for individual cells. a, b, c, and d are the delta values taken as shown in B. Response to IBMX (a to b): 24 cells, 3 experiments; response to EPA (c to d): 11 cells, 2 experiments.