Inhibition by WEB 2086, a PAG-acether antagonist of oedema and peritonitis induced by zymosan in rats.

WEB 2086 reduced the increase in vascular permeability induced by platelet-activating factor (PAF-acether) in rat abdominal skin. Injected alone, WEB 2086 did not modify the oedema induced by zymosan in rat paw. However, administered with methysergide and mepyramine, WEB 2086 reduced the development of this oedema during the first two hours. WEB 2086 also reduced the volume of the exudate induced by zymosan in the peritoneal cavity and its content in leucocytes. Methysergide and mepyramine reduced the volume of the peritoneal exudate. BW755C inhibited the peritoneal accumulation of fluid and of leucocytes. Indomethacin was inactive. The inhibitory effect of WEB 2086 suggests that PAF-acether is involved in the inflammatory responses induced by zymosan in rats beside other endogenous factors such as lipoxygenase products and mast cell amines.