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Endogenous inotropic factor‐induced endothelium‐dependent relaxation of vascular smooth muscle
Author(s) -
Han Chao,
Khatter Jagdish C.
Publication year - 1996
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 - 10.1111/j.1476-5381.1996.tb15391.x
Subject(s) - nitric oxide , medicine , phenylephrine , endocrinology , vasodilation , nitric oxide synthase , chemistry , inotrope , nitroarginine , endothelium , endothelium derived relaxing factor , vascular smooth muscle , endogeny , smooth muscle , blood pressure
1 Possible contractile or relaxation effects of an endogenous inotropic factor (EIF) isolated and purified from porcine heart left ventricle were examined in rat isolated aortic ring preparations. 2 EIF induced a dose‐dependent relaxation of the rat isolated aortic ring preparation pre‐contracted with 0.4 μ m phenylephrine (PE); 200 μl (in 5 ml bath) of EIF caused relaxation of aortic rings by as much as 67.4±4.5%. In another set of experiments, in the presence of 100 μl EIF, the PE concentration‐response contractile curve shifted to the right, the maximal contractile force was reduced by as much as 32.8% and the EC 50 of PE increased from 0.2 to 0.3 μ m . 3 The relaxation effect of EIF was demonstrated to be endothelium‐dependent. Additional experiments demonstrated that EIF‐induced relaxation in an isolated aortic ring could be inhibited by 2 μ m N G ‐nitro‐L‐arginine methyl ester, a nitric oxide synthase inhibitor, suggesting the involvement of nitric oxide in EIF‐induced relaxation of the muscle. 4 Atropine (0.2 μ m ) or indomethacin (10 μ m ) had no significant effect on EIF‐induced relaxation. 5 These data suggest that EIF, a novel endogenous inotrope from porcine myocardium, also acts as an endothelium‐dependent vasodilator substance mediating relaxation in the rat isolated aorta mainly by release of nitric oxide. The possibility of EIF acting through muscarinic receptor and the involvement of prostacyclin were excluded.