Affiliation:
1. Department of Physiology, Downstate Medical Center, State University of New York Brooklyn, New York
Abstract
The possibility that the inotropic action of epinephrine might be mediated through an effect on the excitation-contraction coupling process was explored, using techniques for measurement of isometric tension, together, in some experiments, with recording of the transmembrane potential time course from short lengths of cat papillary muscle. Four observations relevant to this question, have been made: (1) Extracellular calcium concentration can be raised and extracellular sodium concentration lowered to a point at which contraction cannot be further augmented by the addition of epinephrine. (2) The early relaxation induced by epinephrine occurs well in advance of membrane repolarization. This effect is antagonized by increasing calcium concentration, although the action of epinephrine in augmenting developed tension appears to be synergistic with that of calciumion. (3) The length-tension relationship is undiminished in the calcium-rich (8.1 mmoles /liter), sodium-poor (75 mEq/liter) medium. (4) Epinephrine, in a dose (1 to 2 µg/ml) which markedly augments twitch tension, profoundly decreases tension developed by the same preparation during a potassium chloride contracture; this is the case for both the frog ventricle strip and the cat papillary muscle. A preliminary concept of the ionic mechanism of excitation-contraction coupling, compatible with these facts and with some others, is described.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Reference25 articles.
1. Influence de l'adrenaline et de la tyramine sur la contraction du myocarde;KRUTA V.;Arch. Intern. Pharmacodyn.,1938
2. Force-velocity relations in mammalian heart muscle;SONNENBLICK E.;Am. J. Physiol.,1962
3. The mechanism of cardiac stimulation by epinephrine;WIGGERS C. J.;J. Pharmacol. Exptl. Therap.,1927
4. The specific influence of the accelerator nerves on the duration of ventricular systole;WICGERS C. J.;Am. J. Physiol.,1920
5. Regulation of the performance of the heart. In Handbook of Physiology, sec. 2, Circulation, ed. by W. F. Hamilton and P. Dow. Washington, D. C;SARNOFF S. J.;Am. Phys. Soc.,1963
Cited by
75 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献