RANKL-stimulated PGE₂ secretion is compromised in RAW-RacN17 cells. (A) RAW264.7 cells and RAW-RacN17 cells were stimulated with or without RANKL (50 ng/mL) for 8 hours. Culture supernatants were collected and PGE₂ concentration was measured as described in “Materials and methods.” Unstimulated cultures from RAW264.7 and RAW-RacN17 cells secreted similar levels of PGE₂. PGE₂ levels produced by unstimulated cells were given the arbitrary value of 1. Data are expressed as mean (± SD) of triplicates. Similar results were obtained in 2 additional experiments. (B) RAW264.7 cells were pretreated for 30 minutes with indomethacin (10 μM) and celecoxib (100 ng/mL) and stimulated with RANKL for 8 hours. PGE₂ levels were measured as described in panel A. Data are expressed as mean (±SD) of triplicates.