The active state of frog ventricular muscle was determined using graphical, experimental, and instantaneous methods, revealing it is maintained longer in isometric than isotonic contractions.
This study demonstrates multiple methods for determining the active state in frog ventricular muscle, providing insights into indicators of myocardial contractility.
(1) The whole course of the active state was determined by the graphical, experimental and instantaneous methods in the strip preparation of the frog ventricle. These curves were compared with each other.(2) By the graphical method the active state was drawn as the sum of the isometric tension curve, P(t), and the velocity-dependent tension-loss, which was obtained from P(t), converting through the force-velocity curve and the tension-extension curve of SEC. By this method not only the active state during isometric contraction but also during isotonic and afterload contractions were drawn.(3) The force-velocity curves on stretching by the load as well as on shortening were determined at various muscle lengths, applying the controlled release near the peak tension.(4) The tension-extension curve of SEC was directly obtained by the controlled release method. It was independent of temperature.(5) The active state was determined experimentally by plotting the troughs after quick-stretch and the peaks after quick-release. This curve was diminished in the later phase of tension development, compared with the curve obtained by the graphical method.(6) The active state was recorded simultaneously with P(t), as the sum of P(t) and dP/dt, and the changes produced by various inotropic effects were examined.(7) The active state, P(t), dP/dt, and Vmax were discussed as the indicator of myocardial contractility.
MASHIMA et al. (Fri,) reported a other. Graphical, experimental, and instantaneous methods was evaluated on Active state curve of cardiac muscle. The active state of frog ventricular muscle was determined using graphical, experimental, and instantaneous methods, revealing it is maintained longer in isometric than isotonic contractions.