Inflammation induced by latex of Calotropis procera--a new model to evaluate anti-inflammatory drugs

Latex of Calotropis procera was studied for its inflammatory reactions using pedal oedema and air pouch models of inflammation in rats. Subcutaneous injection of aqueous solution (0.1 ml of 1%) of dry latex (DL) into the plantar surface of paw produced significant inflammation. Maximum inflammatory response was obtained 1 h after the injection and was maintained for a further 1 h. The inflammatory response was accompanied by an increase in vascular permeability that reached its maximum within 15 min. Inflammation was also induced in the 6-day-old rat air pouch by injecting a 2.5% solution of DL. The latter model was characterized for the exudate volume and its protein concentration, and wet and dry weights of granuloma. A time-course study indicated that both the exudate volume and the weight of granuloma were at maximum on day 5 after DL injection while the protein concentration peaked on the third day. Further, the two models were also studied for the anti-inflammatory effect of various drugs. It was observed that in the pedal oedema model, phenylbutazone was more effective than prednisolone while almost complete inhibition was produced by mepyramine and cyproheptadine. On the other hand, in the air pouch model, prednisolone was more effective than phenylbutazone in inhibiting the inflammation. Thus, the DL-induced inflammation in different models could be used to evaluate anti-inflammatory drugs.