Platelet-activating factor interaction with the human erythrocyte membrane.

Platelet-activating factor (PAF) is a soluble signal messenger present in blood at nanomolar concentration. PAF has a wide spectrum of biological activities and is produced by and effective in different cell types. Owing to its important physiological role, we wanted to characterize membrane intercalation and interaction of PAF-16 (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine) by studying its capacity to induce during short-term incubations at high concentrations cell shape alterations, phosphatidylserine exposure, and hemolysis in human erythrocytes. Our results showed that PAF-16 at micromolar concentrations rapidly (<or=1 min) induces stable but wash-sensitive echinocytosis and hemolysis, but no substantial phosphatidylserine exposure. In conclusion, our study characterizes PAF-16 as a highly membrane partitioning non-permeable molecule accumulating in the outer membrane leaflet. These membrane interacting properties of PAF should, also at physiological concentrations, be important part of its nature as a membrane affector molecule.