title: Interaction between lymphocytes and platelets in the synthesis of prostacyclin.
abstract: To test the hypothesis that prostacyclin (PGI2) is formed via a biochemical interaction between platelets and lymphocytes, we measured eicosanoids by high performance liquid chromatography (HPLC) and radioimmunoassay (RIA). A distinct 6-keto-prostaglandin F1 alpha (6KPGF1 alpha) peak was noted when [14C]arachidonic acid ([14C]AA) was added to the mixed cell preparations which was increased by pretreating platelets with 1-benzylimidazole (1-BI). Lymphocytes prelabeled with [14C]AA failed to form 6KPGF1 alpha when stimulated with phytohemagglutinin (PHA) or ionophore A23187. When the prelabeled platelets were suspended together with aspirin-treated lymphocytes and stimulated with ionophore, thrombin, or collagen, a 6KPGF1 alpha peak was detected and enhanced by 1-BI. These results were supported by quantifying the 6KPGF1 alpha content in the HPLC-purified fraction by RIA. Adding prostaglandin H2 (PGH2) directly to lymphocytes led to 6KPGF1 alpha production. Platelet aggregation and release were inhibited by lymphocytes in a dose-related manner. We conclude that lymphocytes possess PGI2 synthase activity which is capable of converting platelet-derived PGH2 into PGI2. PGI2 formed is sufficient to inhibit platelet function.
mesh_terms: D015121:6-Ketoprostaglandin F1 alpha / Q000097:blood*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D011464:Epoprostenol / Q000096:biosynthesis*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008214:Lymphocytes / Q000378:metabolism*; D010974:Platelet Aggregation; D011450:Prostaglandin Endoperoxides, Synthetic / Q000378:metabolism; D044262:Prostaglandin H2; D011463:Prostaglandins H / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D007093:Imidazoles; D011450:Prostaglandin Endoperoxides, Synthetic; D011463:Prostaglandins H; D016718:Arachidonic Acid; D012701:Serotonin; C017062:1-benzylimidazole; D044262:Prostaglandin H2; D015121:6-Ketoprostaglandin F1 alpha; D011464:Epoprostenol