title: Carrageenan-stimulated release of arachidonic acid and of lactate dehydrogenase from rat pleural cells.
abstract: Cells isolated from the rat pleural cavity consist mainly of macrophages, mast cells, eosinophils, and lymphocytes. Isolated pleural cells labeled with [14C]arachidonic acid released appreciable amounts (approximately 12%) of radiolabel upon exposure to pharmacological concentrations of carrageenan (1-100 micrograms/ml). The release of radiolabel was decreased by an inhibitor of phospholipase A2 (p-bromophenacyl bromide) but not by an inhibitor of arachidonate cyclooxygenase (indomethacin). The released products were arachidonic acid and, to a much lesser extent, prostaglandin E2 and leukotriene C4. The release of radiolabel was associated with release of cytosolic lactate dehydrogenase over the same range of carrageenan concentrations. Time-course studies indicated that release of radiolabel preceded that of lactate dehydrogenase. Since p-bromophenacyl bromide blocked stimulated release of radiolabel but did not prevent release of lactate dehydrogenase, it is unlikely that increase in arachidonate causes carrageenan-induced cell damage. Nevertheless, the question of whether the activation of phospholipase A2 in the pleural cells, most probably the macrophages, was sufficient to initiate the carrageenan-induced inflammatory response requires further study. Cytotoxicity which was apparent with as little as 5 micrograms/ml of carrageenan, may have been a significant consequence of carrageenan action.
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002351:Carrageenan / Q000494:pharmacology*; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors; D015232:Dinoprostone; D007213:Indomethacin / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D050356:Lipid Metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D010994:Pleura / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011458:Prostaglandins E / Q000378:metabolism; D051381:Rats; D013189:SRS-A / Q000378:metabolism; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D000098:Acetophenones; D001095:Arachidonic Acids; D016861:Cyclooxygenase Inhibitors; D011458:Prostaglandins E; D013189:SRS-A; D016718:Arachidonic Acid; D002351:Carrageenan; D007770:L-Lactate Dehydrogenase; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone; C006821:4-bromophenacyl bromide; D007213:Indomethacin