| Modulation of pacemaker activity in sheep cardiac Purkinje fibers by stimulation of beta-adrenoceptor subtypes. | |
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MedLine Citation:
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PMID: 9062649 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The electrophysiological effects mediated by beta 1- and beta 2-adrenoceptors in spontaneously active sheep cardiac Purkinje fibers were investigated using the non-selective agonist (-)-isoproterenol (IPN) and the selective agonists (-)-noradrenaline (beta 1) and procaterol (beta 2) in the absence and presence of the selective antagonists bisoprolol (beta 1) and ICI 118,551 (beta 2). IPN (0.01 mumol/l) increased the spontaneous rate by 54% and the slope of diastolic depolarization by 68% of the respective control values. Further, IPN increased the action potential duration at -20 mV (APD -20 mV) from 96 to 154 ms, reduced the APD-70 mV by 17% and the duration of the diastole by 39% and slightly hyperpolarized the maximum diastolic potential. These effects were partially inhibited by ICI 118,551 (0.03 mumol/l), diminished by bisoprolol (0.1 mumol/l) and almost completely blocked by the combination of both antagonists. Concentration response curves of IPN were influenced by the selective antagonists as follows: ICI 118,551 (0.03 mumol/l) shifted the curves to the right by 0.2-0.4 log units and increased the slope factor. Bisoprolol (0.1 mumol/l) induced a greater shift to the right by 1.1-1.5 log units. Combination of bisoprolol with ICI 118,551 shifted the curves to the right by 1.5-1.7 log units. Noradrenaline (0.3 mumol/l) elicited similar actions as IPN. Bisoprolol (0.1 mumol/l) shifted the concentration response curves of noradrenaline to the right by 1.1-1.9 log units. Actions of procaterol (0.1 mumol/l) were weak, attained only 15-35% of the maximal effects of IPN and could be blocked by ICI 118,551 (0.03 mumol/l). These results show that the increase of pacemaker activity induced by catecholamines in sheep cardiac Purkinje fibers is predominantly mediated by stimulation of beta 1-receptors. However, contribution of beta 2-receptor mediated effects could be demonstrated. |
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Authors:
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U Thome; F Berger; U Borchard; D Hafner |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Basic research in cardiology Volume: 92 ISSN: 0300-8428 ISO Abbreviation: Basic Res. Cardiol. Publication Date: 1997 Feb |
Date Detail:
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Created Date: 1997-05-22 Completed Date: 1997-05-22 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0360342 Medline TA: Basic Res Cardiol Country: GERMANY |
Other Details:
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Languages: eng Pagination: 25-34 Citation Subset: IM |
Affiliation:
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Institut für Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Germany. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adrenergic alpha-Agonists
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pharmacology Adrenergic beta-Agonists / pharmacology Adrenergic beta-Antagonists / pharmacology Animals Bisoprolol / pharmacology Dose-Response Relationship, Drug Electrophysiology Heart Conduction System / drug effects, physiology* Isoproterenol / pharmacology Norepinephrine / pharmacology Procaterol / pharmacology Propanolamines / pharmacology Purkinje Fibers / drug effects, physiology* Receptors, Adrenergic, beta-1 / metabolism* Receptors, Adrenergic, beta-2 / metabolism* Sheep |
| Chemical | |
Reg. No./Substance:
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0/Adrenergic alpha-Agonists; 0/Adrenergic beta-Agonists; 0/Adrenergic beta-Antagonists; 0/Propanolamines; 0/Receptors, Adrenergic, beta-1; 0/Receptors, Adrenergic, beta-2; 51-41-2/Norepinephrine; 66722-44-9/Bisoprolol; 72332-33-3/Procaterol; 72795-19-8/ICI 118551; 7683-59-2/Isoproterenol |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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