Journal ArticleDOI
Inhibition of the slow inward current by nifedipine in mammalian ventricular myocardium.
M. Kohlhardt,A. Fleckenstein +1 more
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In this paper, Nifedipine (0.5 mg/1 approximately 1.4 X 10(-6) M) depressed upstroke velocity and overshoot of the Ca2+-mediated action potential and reduced the transmembrane slow inward current by about 50%, but the kinetics of inactivation and recovery from inactivation were not affected.Abstract:
In order to elucidate the mode of action of the Ca2+-antagonistic inhibitor nifedipine, its effect on Ca2+-mediated action potentials and transmembrane slow inward current in papillary muscles of guinea pigs and cats was studied. Nifedipine (0.5 mg/1 approximately 1.4 X 10(-6) M) depressed upstroke velocity and overshoot of the Ca2+-mediated action potential and reduced the transmembrane slow inward current by about 50%, but the kinetics of inactivation and recovery from inactivation were not affected. The decrease of upstroke velocity was accompanied by a proportional diminution of isometric contractile force. This indicates that nifedipine exerts its Ca2+-antagonistic effect on excitation-contraction coupling in mammalian ventricular myocardium by inhibition of the transmembrane Ca2+ inward current. The inhibitory action of nifedipine on contractile tension development could be neutralized by an augmentation of the extracellular Ca2+ concentration from 2 mM to 4 mM or by beta-receptor stimulation (isoproterenol) that promotes the transmembrane Ca2+ uptake during excitation. Simultaneously, in the Ca2+-rich medium or under the influence of isoproterenol the upstroke velocity of the Ca2+-mediated action potentials rose even above the initial values which were measured prior to the nifedipine administration.read more
Citations
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Journal ArticleDOI
Comparative pharmacology of calcium antagonists: Nifedipine, verapamil and diltiazem
TL;DR: Nifedipine is a potent, long-acting vasodilator that has proved highly efficacious in relieving anginal symptoms caused by coronary vasospasm, and its value as an antiarrhythmic agent remains to be delineated.
Journal ArticleDOI
Mechanism of calcium channel blockade by verapamil, D600, diltiazem and nitrendipine in single dialysed heart cells
TL;DR: Organic inhibitors of calcium influx prevent outward as well as inward current through cardiac calcium channels but do not slow current activation, and organic drugs show varying degrees of use-dependent block.
Journal ArticleDOI
Antiarrhythmic Agents: The Modulated Receptor Mechanism of Action of Sodium and Calcium Channel-Blocking Drugs
L M Hondeghem,B G Katzung +1 more
TL;DR: This review concentrates on the antiarrhythmic drug literature pertinent to an evaluation of the modulated receptor hypothesis: lidocaine, procainamide, quinidine, diphenylhydantoin, and propranolol.
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Voltage-dependent block of calcium channel current in the calf cardiac Purkinje fiber by dihydropyridine calcium channel antagonists.
TL;DR: The results suggest that dihydropyridines bind preferentially to the inactivated state of the calcium channel, and that the development of usedependent block is related to the ionization constants of the compounds.
Journal ArticleDOI
Structure of the voltage-gated calcium channel Ca v 1.1 at 3.6 Å resolution
TL;DR: The atomic model of the Cav1.1 complex establishes a foundation for mechanistic understanding of excitation–contraction coupling and provides a three-dimensional template for molecular interpretations of the functions and disease mechanisms of Cav and Nav channels.
References
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Specific Pharmacology of Calcium in Myocardium, Cardiac Pacemakers, and Vascular Smooth Muscle
TL;DR: In a wide variety of excitable cells the transmembrane exchange of the monovalent marine cations Na and K can be considered the substantial basis of bioelectric membrane activity, whereas Ca ions are required as mediators when, by this superfi cial process, intracellular reactions such as muscular contraction, glandular secre tion, or liberation of transmitter substances are initiated.
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Differentiation of the transmembrane Na and Ca channels in mammalian cardiac fibres by the use of specific inhibitors
TL;DR: Verapamil and D 600 differ in this respect from common local anesthetic compounds such as xylocaine (lidocaine) or procaine which interfere much more with the transmembrane Na conductivity than with the Ca conductivity.
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Calcium Current and Activation of Contraction in Ventricular Myocardial Fibers
Harald Reuter,George W. Beeler +1 more
TL;DR: In thin bundles of dog ventricular myocardium, a slow inward current could be recorded under voltageclamp conditions and this inward current was influenced by changes in external calcium concentration, but it was not dependent on external sodium concentration.
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Electrical and mechanical responses from ventricular muscle fibers after inactivation of the sodium carrying system.
TL;DR: The electrical and mechanical responses of spontaneously and KCl depolarized ventricular fibers (cat and dog) were studied using a modified sucrose gap technique.
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[On the effect of adrenaline on the cellular Ca-metabolism in the guinea pig atrium].
TL;DR: In this paper, an isolierten, elektrisch gereizten Meerschweinchen Vorhofen with Hilfe des Radioisotops 45Ca untersucht.