title: Inhibition of transmembrane movement and metabolism of platelet activating factor (PAF-acether) by a specific antagonist, BN 52021.
abstract: Incorporation of 1-[3H]-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine ([3H] PAF-acether) into rabbit platelet phosphatidylcholine (PC) was inhibited by a specific antagonist, BN 52021 (IC50 5.6 X 10(-6) M, maximal effect, i.e 70% inhibition, at 10(-4) M). Under the same conditions, [3H] lyso-PAF-acether incorporation remained 9 fold lower, compared to PAF-acether, without any effect of BN 52021. Upon cell lysis, both phospholipids attained the same rate of metabolic conversion, corresponding to a 1.15-fold and a 12-fold increase for PAF-acether and lyso-PAF-acether, respectively. In none of these cases was BN 52021 effective. It is concluded that transmembrane movement of the two phospholipids represents the limiting step of their metabolism. The higher rate of PAF-acether conversion by intact platelets could involve its binding to a membrane receptor, as suggested by the inhibitory effect of BN 52021, the significance of which is discussed.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; D010713:Phosphatidylcholines / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D010972:Platelet Activating Factor / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled
chemical_list: D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; C029271:O-deacetyl platelet activating factor; D010713:Phosphatidylcholines; D010936:Plant Extracts; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; C045856:ginkgolide B