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. Superoxide dismutase (SOD) is a free radical-scavenger with anti-inflammatory activity. In our country there is not a specifically designed instrument to evaluate edema in CIE.
Methods: Edema was induced by intraplantar injection of carraageenan. Fours groups were evaluated: placebo, two different doses of SOD, and Naproxen. Edema was evaluated by a specially designed mercury plethismograph. 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-inflammatory activity throughout early, late, and very late phases. Naproxen was more effective than SOD during first and second phase, however this difference disappeared during the third phase. In terms of equimolar basis the enzyme appeared 1,800 time more potent than Naproxen. Mercury plethysmometer performance was fine.
Conclusions: The anti-inflammatory activity of SOD and Naproxen 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 may be indeed an alternative treatment in inflammatory diseases.