Superoxide dismutase and Naproxen (R) in the very late phase of carrageenan induced edema in rats

Background. Rat hind-foot carrageenan induced edema (CIE) is a widely used model to evaluate anti-inflammatory drugs. It shows two well-defined phases , however a third not fully characterized phase has been observed. Superoxi de dismutase (SOD) is a free radical-scavenger with anti-inflammatory activ ity. In our country there is not a specifically designed instrument to eval uate edema in CIE. Methods. Edema was induced by intraplantar injection of carraageenan. Fours groups were evaluated: placebo, two different doses of SOD, and Naproxen(R). Edema was evaluated by a specially designed mercury p lethismograph. Intensity of the inflammatory reaction was determined during the classical early and late phases and during the third very late phase. Results. All treatments, but higher dose of SOD, showed good anti-inflammat ory activity throughout early, late, and very late phases. Naproxen(R) was more effective than SOD during first and second phase, however this differe nce disappeared during the third phase. In terms of equimolar basis the enz yme appeared 1,800 time more potent than Naproxen(R). Mercury plethysmomete r performance was fine. Conclusions. The anti-inflammatory activity of SOD and Naproxen(R) is extended until the very late phase in the CIE model. In this bioassay, this long lasting activity of the enzyme should be ascribed to a mechanism supplementary to its free radical-scavenger property. SOD ma y be indeed an alternative treatment in inflammatory diseases.