Cutaneous and pulmonary histopathological responses to platelet activating factor (Paf-acether) in the guinea-pig

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Abstract
The effect of synthetic Paf‐acether has been studied in guinea‐pig skin, following intradermal injection, and in guinea‐pig lung, following intravenous administration. Histopathological responses to Paf‐acether were assessed by both light microscopy and electron microscopy. In addition, plasma protein extravasation and platelet accumulation were quantitatively assessed using radiolabelling techniques. Intradermal injection of Paf‐acether, but not lyso‐Paf, elicited acute increased vascular permeability, accompanied by intravascular accumulation of platelets and neutrophils. There was evidence, 2–8 h after intradermal injection of Paf‐acether, of perivascular infiltration with neutrophils. At 24 h there was a mixed cellular infiltrate comprising mononuclear cells in addition to neutrophils. Following systemic administration of Paf‐acether, aggregates of platelets in close association with neutrophils were evident within the pulmonary vasculature. Intravenous injection of Paf‐acether, but not lyso‐Paf, caused intrathoracic accumulation of radiolabelled platelets. These results suggest that Paf‐acether has properties consistent with those of a mediator of inflammation.