Effect of synthetic phospholipids on platelet aggregation and serotonin release

1-O-Hexadecyl-2-O-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor, PAF) is known to stimulate platelet aggregation and serotonin release in concentrations ranging from 10(-10)-10(-5) M. Since a variety of synthetic PAF analogues are potent antineoplastic agents in vitro and in vivo, it was the aim of this study to examine the PAF-like activity of 15 analogues, including 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) and a thioether analogue. In platelet-rich plasma from human blood, platelet aggregation and serotonin release were studied to compare the effects of PAF and the analogues. Platelet function was controlled by testing their response to adenosine diphosphate, arachidonic acid, collagen and epinephrine. Our results show that only PAF was able to induce platelet aggregation and serotonin release in concentrations from 10(-9) to 10(-5) M, whereas all the tested analogues up to a concentration of 10(-3) M failed to induce these effects.