title: The mechanism of action of leukotrienes C4 and D4 in guinea-pig isolated perfused lung and parenchymal strips of guinea pig, rabbit and rat.
abstract: The biological actions of pure slow-reacting substance of anaphylaxis (SRS-A) from guinea-pig lung, pure slow-reacting substance (SRS) from rat basophilic leukaemia cells (RBL-1) and synthetic leukotrienes C4 (LTC4) and D4 (LTD4) have been investigated on lung tissue from guinea pig, rabbit and rat. In the guinea pig, the leukotrienes released cyclo-oxygenase products from the perfused lung and contracted strips of parenchyma. The effects of SRS-A, SRS and LTD4 were indistinguishable. LTC4 and LTD4 had similar actions although LTD4 was more potent than LTC4. Indomethacin (1 microgram/ml) inhibited the release of cyclo-oxygenase products from perfused guinea-pig lung and caused a marked reduction in contractions of guinea-pig parenchymal strips (GPP) due to LTC4 and LTD4. The residual contraction of the GPP was abolished by FPL 55712 (0.5 - 1.0 microgram/ml). It appears, therefore, that a major part of the constrictor actions of LTC4 and LTD4 in guinea-pig lung are mediated by myotropic cyclo-oxygenase products, i.e. thromboxane A2 (TxA2) and prostaglandins (PGs). In rabbit and rat lung, however, SRS-A, SRS and the leukotrienes were much less potent in contracting parenchymal strips and there was little evidence of the release of cyclo-oxygenase products. FPL 55712 at a concentration of 1 microgram/ml failed to antagonise leukotriene-induced contractions.
mesh_terms: D000818:Animals; D012898:Autacoids / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013189:SRS-A / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000378:metabolism
chemical_list: D012898:Autacoids; D011453:Prostaglandins; D013189:SRS-A; D013928:Thromboxane A2; D011451:Prostaglandin-Endoperoxide Synthases