Effect of platelet-activating factor on leukocyte adhesion to microvascular endothelium. Time course and dose-response relationships.

The hamster cheek pouch microcirculation was used to investigate the effects of platelet-activating factor (PAF) on leukocyte adhesion to microvascular walls by means of intravital microscopy. PAF was applied topically at concentrations ranging from 10(-11) to 10(-5) M. An inverse relationship between PAF concentration and number of adhering white cells per 100-microns length was found in venules ranging in diameter from 10 to 60 microns (grouped into 10-microns intervals). Importantly, the PAF-induced adhesion of leukocytes lasted for the 3-h experimental period. We postulate that induction of leukocyte adhesion to venular endothelium is an important role of PAF in inflammatory processes.