PRODUCTION OF AN ANTI-INFLAMMATORY SUBSTANCE AT A SITE OF INFLAMMATION

The anti-inflammatory effect of various substances was measured in rats implanted with cotton wool pellets. Injection or implantation of irritant materials decreased the deposition of granulation tissue on the pellets. As the amount of irritant material increased there was a corresponding decrease in the amount of tissue deposited on the pellets. There is evidence that this could not be explained by a limit to the amount of granulation tissue available within the body, and competition for it between the cotton pellets and the implanted substances. An alternative hypothesis that an anti-inflammatory substance is produced at the site of irritation (the site of implantation of the irritant substance, such as polyester sponges) was investigated. The evidence obtained supports this hypothesis. Inflammatory exudate, squeezed from polyester sponges which had been implanted subcutaneously in the backs of adrenalectomized rats. The substance responsible for this effect is probably not a steroid, and is not normally present in the plasma of adrenalectomized animals. There is, however, some (although not conclusive) evidence that it is present in the plasma of animals in which sponges have been implanted. It does not appear to be produced by incubation in vitro of plasma with sponge. The significance of these observations is discussed.