Mediators of the inflammation induced in the rat paw by carrageenin.

1. The time course of oedema formation in rats caused by injection of carrageenin into the paw was followed for 5.5 hours. Intact or adrenalectomized rats which had previously been injected with ellagic acid or saliva to reduce considerably the concentration of blood kininogens, or with methysergide to antagonize 5-hydroxytryptamine (5-HT) showed a reduced inflammatory response. It was concluded that kinins and 5-HT contributed significantly to oedema formation during this period.2. Mepyramine alone had no effect on oedema formation, but in combination with ellagic acid treatment, with or without methysergide, it caused a reduction suggesting that histamine played a minor role in oedema formation during the first 3 hours.3. Vascular permeability studies indicated that injection of ellagic acid did not interfere with the normal responses in skin to intradermal injections of histamine, 5-HT, bradykinin or compound 48/80. Mepyramine and methysergide, at the doses used in the carrageenin experiments, completely antagonized histamine and 5-HT, respectively, and did not affect the skin responses of bradykinin.4. Treatment in vivo with ellagic acid or rat saliva was equally effective in reducing plasma kininogen concentrations by an amount equivalent to more than 10 times the quantity of substrate 1 measured by Gautvik & Rugstad (1967).5. Rat saliva, but not ellagic acid, lowered complement levels by approximately 20%.