title: Decay of the activating signal after platelet stimulation with 1-0-alkyl-2-acetyl-SN-glycero-3-phosphorylcholine: changes in calcium permeability.
abstract: The decay of the platelet-activating signal after platelet stimulation with the platelet-activating factor 1-0-alkyl-2-acetyl-SN-glycero-3-phosphorylcholine (AGEPC) was examined. Washed human platelets in calcium-poor buffer were stimulated with AGEPC followed 0.25 to 10 min later by reconstitution with 1.8 mM calcium. AGEPC did not induce platelet aggregation in calcium-poor buffer but aggregation occurred upon addition of calcium. The capacity of calcium-reconstitution to elicit platelet aggregation decayed rapidly after platelet exposure to AGEPC (T 1/2 = 1 min). A parallel decay of AGEPC-induced increased calcium permeability (R = 0.93) was demonstrated using the fluorescent probe Quin 2. Studies with calcium channel blockers suggest that AGEPC opens a calcium channel which is distinct from those present in unstimulated platelets.
mesh_terms: D000328:Adult; D000634:Aminoquinolines; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood* / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects*; D005456:Fluorescent Dyes; D006801:Humans; D007700:Kinetics; D010972:Platelet Activating Factor / Q000494:pharmacology*
chemical_list: D000634:Aminoquinolines; D005456:Fluorescent Dyes; D010972:Platelet Activating Factor; C035739:Quin2; D002118:Calcium