Related Experiment Video

Updated: Aug 9, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
06:22

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice

Published on: September 17, 2015

Effects of Ca antagonist on the contractile force in glycerinated dog heart muscles

Y Maruyama, H Okayama, N Ishide

    Pflugers Archiv : European Journal of Physiology
    |October 1, 1982
    PubMed

    Insights

    Calcium (Ca) antagonists like verapamil significantly enhance cardiac muscle contractile force. This study shows these agents potentiate contractility, increasing developed tension and contraction speed in canine heart muscle preparations.

    Area of Science:

    • Cardiovascular Physiology
    • Pharmacology
    • Muscle Contraction

    Background:

    • Calcium antagonists are known to affect cardiac function.
    • Their precise impact on the cardiac contractile apparatus requires further elucidation.

    Purpose of the Study:

    • To investigate the effect of calcium (Ca) antagonists on the contractile apparatus of cardiac muscle.
    • To determine if Ca antagonists potentiate or inhibit cardiac muscle contractility.

    Main Methods:

    • Glycerinated cardiac muscle preparations from canine hearts were used.
    • Isometric contractions were induced using control solutions and solutions containing verapamil or diltiazem hydrochloride.
    • Maximal developed tension (Po) and rate of tension development (dT/dt) were measured at varying calcium concentrations (pCa).

    Main Results:

    • Verapamil significantly enhanced maximal developed tension (Po) and dT/dt in a dose-dependent manner.
    • Diltiazem hydrochloride also demonstrated contractile potentiation.
    • Verapamil shifted the pCa-tension relationship leftward, indicating increased myofilament sensitivity to Ca2+.

    Conclusions:

    • Calcium (Ca) antagonists, specifically verapamil and diltiazem, act as potentiating agents of cardiac contractile force.
    • These findings suggest a novel role for Ca antagonists in augmenting myocardial contractility through enhanced Ca2+ sensitivity.

    More Related Videos

    Preparation of Human Myocardial Tissue for Long-Term Cultivation10:58

    Preparation of Human Myocardial Tissue for Long-Term Cultivation

    Published on: June 2, 2022

    Analysis of Cardiac Contractile Dysfunction and Ca2+ Transients in Rodent Myocytes07:32

    Analysis of Cardiac Contractile Dysfunction and Ca2+ Transients in Rodent Myocytes

    Published on: May 25, 2022

    Related Concept Videos

    G-Protein Gated Ion Channels01:21

    G-Protein Gated Ion Channels

    GPCRs are primarily responsible for our sense of smell, taste, and vision.  The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
    Sensory organs,...
    Relaxation of Skeletal Muscles01:29

    Relaxation of Skeletal Muscles

    The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
    When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
    Specialized Characteristics of Cardiac Muscles01:27

    Specialized Characteristics of Cardiac Muscles

    The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
    Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...
    Smooth Muscle Contraction01:25

    Smooth Muscle Contraction

    Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
    The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
    Antihypertensive Drugs: Action of Calcium Channel Blockers01:18

    Antihypertensive Drugs: Action of Calcium Channel Blockers

    Calcium ions are essential to contract smooth muscle cells in blood vessels. They enter these cells through voltage-dependent calcium channels, specifically L-type calcium channels in the cell membrane. These L-type calcium channels are integral to the excitation-contraction coupling process in smooth muscle. When a stimulus is received by smooth muscle cells, their membrane depolarizes. This alteration in membrane potential instigates the opening of L-type calcium channels. As a result,...
    Heart Failure Drugs: Inotropic Agents01:26

    Heart Failure Drugs: Inotropic Agents

    Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...