Pre-treatment with α-hederin increases β-adrenoceptor mediated relaxation of airway smooth muscle.
Preparations of ivy leaves dry extract with secretolytic and bronchiolytic efficacy are widely used for the treatment of acute and chronic obstructive airway diseases. The mechanism by which ivy preparations improve lung functions is not fully understood. Here, we tested the influence of the three main saponins of ivy, α-hederin, hederacoside C and hederagenin, on the contraction and relaxation behaviour of isolated bovine tracheal smooth muscle strips by isometric tension measurements. None of the tested compounds altered histamine or methacholine-induced contraction of the smooth muscle strips. In contrast, the isoprenaline-induced relaxation of 100μM methacholine precontracted muscle strips was significantly enhanced when pre-treated with 1μM of α-hederin for 18h. The pre-treatment with hederacoside C or hederagenin had no effect on isoprenaline-induced relaxation. For the first time the bronchiolytic effect of α-hederin was demonstrated by isometric tension measurements using bovine tracheal smooth muscle strips. α-Hederin increases isoprenaline-induced relaxation indirectly, probably by inhibiting heterologous desensitization induced by high concentrations of muscarinic ligands like methacholine.
Wolf
Anne
A
Institute of Biochemistry and Molecular Biology, Rheinische Friedrich-Wilhelms-Universität, Nussallee 11, 53115 Bonn, Germany.
Gosens
Reinoud
R
Meurs
Herman
H
Häberlein
Hanns
H
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001993:Bronchodilator Agents / Q000494:pharmacology*; D002417:Cattle; D004357:Drug Synergism; D035981:Hedera / Q000737:chemistry; D006632:Histamine; D007545:Isoproterenol / Q000494:pharmacology*; D016210:Methacholine Chloride; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves; D012503:Saponins / Q000494:pharmacology*; D014132:Trachea
D000318:Adrenergic beta-Agonists; D001993:Bronchodilator Agents; D010936:Plant Extracts; D012503:Saponins; C010177:beta-hederin; D016210:Methacholine Chloride; D009828:Oleanolic Acid; D006632:Histamine; D007545:Isoproterenol