High CCK concentration activates PKA pathway which attenuates LPS-induced iNOS expression by peritoneal macrophages. To associate changes on intracellular cAMP and PKA activation with LPS-induced iNOS expression, the macrophage culture was incubated with PKA inhibitor (H-89) (10−10–10−7 M) for 30 min before the addition of CCK at 10−6 M (a and b). Thirty minutes later, cells were stimulated by LPS (1 μg/mL) (time zero). The culture supernatant was collected for nitrite quantification by Griess method (a) and the iNOS synthesis was determined in cell lysates by ELISA (b). Data is a representative of three independent experiments with similar results. Values are expressed as means ± S.E.M. 4–12 samples per group. * versus saline, # versus LPS, and a versus respective CCK group.
