[Influence of hexobendine, prenylamine and verapamil on the contractile response of isolated rabbit left atria and aortae to calcium (author's transl)].
In isolated rabbit left atria driven electrically at a frequency of 30/min, the contraction was abolished by increasing external K+ concentrations from 5.4 to 22mM. Addition of isoproterenol (10(-6)M) restored the atrial contraction and the magnitude of contractions increased by raising external concentrations of Ca++ to 4.4 and 6.6. mM. Hexobendine attenuated the magnitude of contractions restored by isoproterenol and excess Ca++ in a dose-dependent manner, as did prenylamine and verapamil. Hexobendine did not significantly influence the membrane depolarization induced by excess K+ and there was no evidence of a beta-adrenergic blocking action. In helical strips of rabbit aortae exposed to Ca++-free media and depolarized by excess K+, the addition of Ca++ caused a marked contraction. Hexobendine, prenylamine and verapamil caused a dose-related attenuation of the Ca++-induced contraction. Relative potencies of the inhibition by hexobendine, prenylamine and verapamil were 1:16.5:100. Inhibitory effects of these drugs were partially antagonized by excess Ca++. Greater attenuation of the contractile response to 25 mM K+ than the response to 2 X 10(-6)M noradrenaline was observed in preparations treated with hexobendine. It may be concluded that interference with the influx of Ca++ across cell membrane in atrial muscles and aortic smooth muscles participates in the inhibition of contractility by hexobendine.
D000818:Animals; D001011:Aorta / Q000187:drug effects; D001565:Benzoates / Q000494:pharmacology*; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006325:Heart Atria / Q000187:drug effects*; D006592:Hexobendine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D011188:Potassium / Q000037:antagonists & inhibitors; D011299:Prenylamine / Q000494:pharmacology*; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology*
D001565:Benzoates; D006592:Hexobendine; D014700:Verapamil; D011299:Prenylamine; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine