Summary
Myocardial contractility can be regulated by two types of control mechanism. A “tonic control mechanism”, which allows the heart to respond to sustained changes in circulatory dynamics, appears to operate through changes in the structure of various constituents of the myocardium, best understood of these being changes in the myosin molecule that cause alterations in both myosin ATPase activity and contractility. Beat-to-beat changes in myocardial contractility are affected by a “phasic control mechanism” that involves changes in at least five calcium fluxes in the myocardium. The effects of catecholamines, many of which appear to be mediated by cyclic AMP, can be understood in terms of the modification of several of the calcium fluxes involved in the phasic control of myocardial contractility.
Zusammenfassung
Die myokardiale Kontraktilität kann durch zwei Typen von Kontroll-mechanismen reguliert werden. Ein „tonischer Kontrollmechanismus”, der den Herzen die Anpassung an langdauernde Veränderungen des Kreislaufs erlaubt, scheint auf Änderungen in der Struktur verschiedener Bestandteile des Myokards zu beruhen, wobei die klarsten Vorstellungen Veränderungen des Myosinmoleküls betreffen, die ihrerseits Änderungen sowohl der Myosin-ATPase-Aktivität als auch der Kontraktilität verursachen. Änderungen der myokardialen Kontraktilität von Schlag zu Schlag werden durch einen „phasischen Kontrollmechanismus” bewirkt, der wenigstens 5 verschiedene Ca-Ströme im Myokard einbezieht. Die Effekte der Katecholamine, von denen viele offenbar durch zyklisches AMP vermittelt werden, lassen sich als Modifikation verschiedener Ca-Ströme erfassen, die bei der „phasischen Kontrolle” der myokardialen Kontraktilität eine Rolle spielen.
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With 1 figure and 2 tables
The work from the Author's laboratory cited in the article was supported by a Grant-in-Aid from the New York Heart Association and U.S. Public Health Service Research Grants HL-13191 and HL-18801 from the National Heart and Lung Institute.
Dr.Katz isPhilip J. andHarriet L. Goodhart Professor of Medicine (Cardiology). This article was written during the tenure of a Senior U.S. Scientist Award from the Alexander von Humboldt Stiftung, Bonn-Bad Godesberg, Bundesrepublik Deutschland.
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Katz, A.M. “Tonic” and “phasic” mechanisms in the regulation of myocardial contractility. Basic Res Cardiol 71, 447–455 (1976). https://doi.org/10.1007/BF01909761
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DOI: https://doi.org/10.1007/BF01909761