Edema was induced in one ear of male mice of the CFLP strain with solutions of different skin irritants (croton oil 10 mu L/35 mu g, dithranol 20 mu L/30 mu g, capsaicin 10 mu L/40 mu g or arachidonic acid to 10 mu L/2 mg per ear). Edema, determined by the edema-disk gravimetric technique, was inhibited in a dose-dependent manner by the intraperitoneally administered prostaglandin antagonists polyphloretin phosphate (PPP) or di-4-phloretin phosphate (DPP). With croton oil-induced mouse ear edema, DPP 10 mg/kg caused a 38% inhibition, PPP 25 mg/kg a 33% inhibition. With dithranol-induced edema DPP 0.5 mg/kg caused a 57% inhibition, while PPP 25 mg/kg was needed to exert a similar effect. Doses of DPP and PPP needed to cause a >40% inhibition of edema were 10 mg/kg and 25 mg/kg, respectively for capsaicin, and 25 mg/kg and 200 mg/kg for arachidonic acid. The inhibition of the ear edema by the phloretin derivatives was: dithranol > croton oil > capsaicin > arachidonic acid. This probably reflects the different contributions of prostaglandins to the inflammation.
