Failure of anti-inflammatory steroids to inhibit prostaglandin production by rat polymorphonuclear leucocytes.

1 Like rabbit polymorphonuclear (PMN) leucocytes, rat peritoneal glycogen-induced PMN leucocytes produced much greater amounts of prostaglandin when incubated with killed bacteria than in the absence of phagocytosable material. 2 Rat PMN leucocytes mainly prostaglandin E2 (PGE2), in amounts up to 17 ng/10(6) cells in 90 min incubation, some 25 times the amount produced by resting cells. 3 Indomethacin and meclofenamic acid inhibited prostaglandin production by resting and phagocytosing cells, the IC50 being of the order of 10(-6) to 10(-7) M for both drugs. 4 Hydrocortisone and dexamethasone at concentrations up to 10(-4) M did not cause significant dose-related inhibition of prostaglandin production in this system. 5 It is suggested that the phagocytosing PMN leucocyte is insensitive to the action of anti-inflammatory steroids with respect to prostaglandin production.