title: Echinacoside induces rat pulmonary artery vasorelaxation by opening the NO-cGMP-PKG-BKCa channels and reducing intracellular Ca2+ levels.
abstract: OBJECTIVE
  Sustained pulmonary vasoconstriction as experienced at high altitude can lead to pulmonary hypertension (PH). The main purpose of this study is to investigate the vasorelaxant effect of echinacoside (ECH), a phenylethanoid glycoside from the Tibetan herb Lagotis brevituba Maxim and Cistanche tubulosa, on the pulmonary artery and its potential mechanism.
  
  
  METHODS
  Pulmonary arterial rings obtained from male Wistar rats were suspended in organ chambers filled with Krebs-Henseleit solution, and isometric tension was measured using a force transducer. Intracellular Ca(2+) levels were measured in cultured rat pulmonary arterial smooth muscle cells (PASMCs) using Fluo 4-AM.
  
  
  RESULTS
  ECH (30-300 μmol/L) relaxed rat pulmonary arteries precontracted by noradrenaline (NE) in a concentration-dependent manner, and this effect could be observed in both intact endothelium and endothelium-denuded rings, but with a significantly lower maximum response and a higher EC50 in endothelium-denuded rings. This effect was significantly blocked by L-NAME, TEA, and BaCl2. However, IMT, 4-AP, and Gli did not inhibit ECH-induced relaxation. Under extracellular Ca(2+)-free conditions, the maximum contraction was reduced to 24.54%±2.97% and 10.60%±2.07% in rings treated with 100 and 300 μmol/L of ECH, respectively. Under extracellular calcium influx conditions, the maximum contraction was reduced to 112.42%±7.30%, 100.29%±8.66%, and 74.74%±4.95% in rings treated with 30, 100, and 300 μmol/L of ECH, respectively. After cells were loaded with Fluo 4-AM, the mean fluorescence intensity was lower in cells treated with ECH (100 μmol/L) than with NE.
  
  
  CONCLUSIONS
  ECH suppresses NE-induced contraction of rat pulmonary artery via reducing intracellular Ca(2+) levels, and induces its relaxation through the NO-cGMP pathway and opening of K(+) channels (BKCa and KIR).
authors: 1] Department of Pharmacology, School of Life Science and Biopharmaceutics, Shenyang Pharmaceutical University, Shenyang 110016, China [2] Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China [3] School of Pharmacy, Qinghai University for Nationalities, Xining 810007, China.
authors: Xiang-yun
authors: XY
authors: Gai
authors: Qinghai Entry-Exit Inspection and Quarantine Bureau, Xining 810001, China.
authors: Yu-hai
authors: YH
authors: Wei
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Wei
authors: W
authors: Zhang
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Ta-na
authors: TN
authors: Wuren
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Ya-ping
authors: YP
authors: Wang
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Zhan-qiang
authors: ZQ
authors: Li
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Shou
authors: S
authors: Liu
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Lan
authors: L
authors: Ma
authors: Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Dian-xiang
authors: DX
authors: Lu
authors: 1] Department of Pharmacology, School of Life Science and Biopharmaceutics, Shenyang Pharmaceutical University, Shenyang 110016, China [2] Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Yi
authors: Y
authors: Zhou
authors: 1] Department of Pharmacology, School of Life Science and Biopharmaceutics, Shenyang Pharmaceutical University, Shenyang 110016, China [2] Research Center for High Altitude Medicine, Medical College of Qinghai University, Xining 810001, China.
authors: Ri-li
authors: RL
authors: Ge
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology; D006027:Glycosides / Q000494:pharmacology*; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000819:agonists* / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects* / Q000201:enzymology; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D006027:Glycosides; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; C060297:echinacoside; D009638:Norepinephrine