Involvement of K+ movements in the membrane signal induced by PAF-acether.
We investigated the effects of PAF-acether and its specific antagonist BN 52021 on Na+ and K+ transport systems in human red cells and mouse macrophages. PAF-acether and BN 52021 exhibited specific and opposite effects on a Cs+-stimulated, K+ efflux in human red cells. PAF-acether increased and BN 52021 decreased the apparent dissociation constant for external Cs+ without significant effects on the maximal rate of K+ translocation. In mouse macrophages, PAF-acether stimulated a quinidine-sensitive K+ efflux. In the presence of the Ca2+-ionophore A 23187, PAF-acether and BN 52021 showed opposite effects (stimulation and inhibition respectively). For most cells, membrane potential is dependent on K+-permeability. In addition, opening of potential-dependent Ca2+ channels appears to be associated with cell activation in several models. We thus propose that the specific interaction of PAF-acether with a K+:K+ exchange increases Ca2+ uptake through transitory changes in membrane potential. This in turn may lead to a more permanent membrane hyperpolarization through to opening of Ca2+ dependent, K+ channels.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002586:Cesium / Q000494:pharmacology; D004224:Diterpenes; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D046934:Ginkgolides; D006801:Humans; D007700:Kinetics; D007783:Lactones; D008094:Lithium / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008954:Models, Biological; D010936:Plant Extracts / Q000494:pharmacology*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; D010936:Plant Extracts; D010972:Platelet Activating Factor; D002586:Cesium; D008094:Lithium; D012964:Sodium; C045856:ginkgolide B; D011188:Potassium