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The ACh‐induced contraction in rat aortas is mediated by the Cys Lt 1 receptor via intracellular calcium mobilization in smooth muscle cells
Author(s) -
Mazzetti Luca,
FranchiMicheli Sergio,
Nistri Silvia,
Quattrone Silvia,
Simone Ruggero,
Ciuffi Mario,
Zilletti Lucilla,
Failli Paola
Publication year - 2003
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705087
Subject(s) - contraction (grammar) , endocrinology , acetylcholine , medicine , phenylephrine , chemistry , receptor , fura 2 , muscle contraction , calcium in biology , vascular smooth muscle , calcium , ryanodine receptor , biology , biochemistry , cytosol , enzyme , blood pressure , smooth muscle
Our previously published data indicate that an endogenously produced 5‐lipoxygenase metabolite can strongly contract isolated endothelium‐preserved rat aortic strips when cyclo‐oxygenase isoenzymes are inhibited. Therefore, we decided to investigate if cysteinyl‐containing leukotrienes (Cys Lts) are involved in this endothelium‐dependent contraction. The isometric contraction of endothelium‐preserved rat aortic strips was recorded in preparations preincubated with 5 μ M indomethacin and precontracted with phenylephrine, adjusting resting tension at 0.7 g. Acetylcholine (ACh) contracted control strips. Montelukast and MK‐571, selective type 1 Cys Lts receptor (Cys Lt 1 ) antagonists and the Cys Lt 1 /Cys Lt 2 (type 2 Cys Lts receptor) antagonist BAYu9773 dose‐dependently prevented ACh‐induced contraction, their IC 50 s being 2.2, 3.1 and 7.9 n M respectively. The leukotriene B4 receptor antagonist U75302 was far less potent (IC 50 1.5 μ M ). In rat aorta smooth muscle cells (RASMs), Western blot analysis showed the presence of Cys Lt 1 and Cys Lt 2 receptors, the Cys Lt 1 receptor being predominantly expressed. In fura‐2 loaded RASMs, LTD4 (0.01–100 n M ) and LTC4 (200–800 n M ) dose‐dependently increased intracellular calcium concentration ([Ca 2+ ] i ). Montelukast (1–100 n M ) reduced LTD4‐induced [Ca 2+ ] i increase, its IC 50 being approximately 10 n M . BAY u9773 exhibited significantly low effectiveness. LTD4 (10 n M ) induced a redistribution of smooth muscle actin fibres throughout the cytoplasm as visualized by confocal microscopy. In conclusion, Cys Lt 1 activation by endogenously produced Cys Lts, can contract rat aortas, while Cys Lt 2 only marginally influences aortic tone. Intracellularly, this effect is mediated by an increase in [Ca 2+ ] i . Therefore, Cys Lts, by inducing vascular contraction, can contribute to systemic hypertension.British Journal of Pharmacology (2003) 138 , 707–715. doi: 10.1038/sj.bjp.0705087