Figure 4.

EP2 and EP4 receptor activation by PGE₂ suppresses H₂O₂ production in AMs through a cAMP-dependent process. Rat AMs (5 × 10⁵) were plated and preincubated with: (A) EP2 receptor antagonist, AH-6809 (100 μM), or the EP4 receptor antagonist, Ono-AE3-208 (1 μM), for 20 minutes; (B) EP2 receptor agonist, butaprost free acid (1 μM), or the EP4 receptor agonist, Ono-AE1-329, for 5 minutes; or (C) AC inhibitor, SQ 22536 (10 μM), for 20 minutes, with or without PGE₂, followed by infection with 50:1 opsonized K. pneumoniae for 1 hour. The H₂O₂ concentration in medium was determined as described in Materials and Methods. Results represent the mean (± SE) of quadruplicate values from one of three representative experiments. *P < 0.05 versus control; ^#P < 0.05 versus K. pneumoniae group by ANOVA.