Activation of guinea pig peritoneal macrophages by platelet activating factor (PAF) and its

The platelet activating factor (PAF: l-0-alkyl-2-0-acetyl-.w-glycero-3-phospho-choline) and its analogs were examined to determine their effects on guinea pig peritoneal macrophages. 1. PAF activated macrophages, but its effect on macrophages was much weaker than that observed on platelets: the concentration required for 50 % maximum activation was 8.5 x 10~6 M for macrophages and 2.9 x 10~10 M for platelets. 2. Three PAF agonists, l-0-octadecyl-2-O-(Ar,A'-dimethylcarbamoyl)-glycero-3-phosphocholine (Compound I), l-0-octadecyl-2-acetamido-2-deoxy-glycero-3-phos-phocholine (Compound II), and l-O-octadecyl-2-O-methyl-glycero-3-phosphocholine (Compound III), showed higher activity in stimulating macrophage function than PAF. The abilities of these non-metabolizable PAF agonists to activate macrophage paralleled their relative potency to induce platelet activation. 3. The sn-3 enantiomers of PAF and Compound III exhibited activity, while the sn- \ did not. By comparing the activities of derivatives of Compound III, it was shown that the long-chain alkyl-ether group in the glycerol-1 position, a relativel