title: The enantiomer and the positional isomer of platelet-activating factor.
abstract: We have compared for rabbit platelet aggregating and desensitizing activity two different preparations of platelet-activating factor (PAF-acether) (1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine) and of its enantiomer (3-O-alkyl-2-O-acetyl-sn-glycero-1-phosphocholine). After phospholipase A2 treatment, the unnatural enantiomers appeared about 3000-fold less active than PAF-acether, a result which definitively establishes the stereospecificity of the mode of action of this mediator. A new structural analog of PAF-acether, 1-O-hexadecyl-3-O-acetyl-sn-glycero-2-phosphocholine, was isolated and characterized. It was a weak platelet agonist, stressing further the importance for PAF-acether activity of the acetyl group at position 2 of the glycerol.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D055598:Chemical Phenomena; D002621:Chemistry; D066298:In Vitro Techniques; D007536:Isomerism; D010743:Phospholipids / Q000097:blood; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects; D011817:Rabbits; D013237:Stereoisomerism
chemical_list: D010743:Phospholipids; D010972:Platelet Activating Factor