Mechanisms of phytohaemagglutinin-P-, concanavalin-A- and kaolin-induced oedemas in the rat.

Subplantar administration of either Phytohaemagglutinin-P (PHA), Concanavalin-A (Con A) or kaolin into the rat hind paw produced a dose related oedema which was still present at 48 h. Both of the lectins were more inflammagenic than kaolin on a weight per weight basis. As a result of studies using mediator inhibitors and depletors it appears that 5HT, but not histamine, may play a role in the early phases (0.5-1.5 h) of both PHA and Con A responses. Neither mediator appears to be involved in the kaolin oedema. Kinins are also likely mediators of the inflammatory response to all three irritants and could be detected in irritant injected air blebs in the rat. Prostaglandins are unlikely to play a significant role in PHA or Con A oedema since indomethacin-induced inhibition of their synthesis has only a slight inhibitory effect on the lectin induced paw oedemas and only small amounts of prostaglandin-like material could be detected in PHA or Con A blebs. However, kaolin oedema appears to have a significant prostaglandin component since large amounts of prostaglandin-like materials were detected in kaolin blebs and also indomethacin reduced the kaolin induced paw oedema. Other mediators of the inflammatory process such as complement are likely to be involved in all three irritant induced oedemas.