Calcium equally increases the internal calcium recirculation fraction before and after β-blockade in canine left ventricles

  title={Calcium equally increases the internal calcium recirculation fraction before and after $\beta$-blockade in canine left ventricles},
  author={Shingo Hosogi and Junichi Araki and Yi Syuu and Shunsuke Suzuki and Satoshi Mohri and Takeshi Mikane and Hiromi Matsubara and Tohru Ohe and Masahisa Hirakawa and Hiroyuki Suga},
  journal={Heart and Vessels},
SummaryWe studied whether intracoronary Ca administration after β-blockade would increase the internal Ca recirculation fraction (RF) analogously to the Ca administration before β-blockade. This was performed in excised cross-circulated canine hearts. We analyzed the exponential decay component of the postextrasystolic potentiation (PESP) following a spontaneous extrasystole. All the PESPs decayed in alternans with atrial pacing at a constant rate. We obtained the time constant (τe) of the… 
Total Ca handling in canine mild Ca overload failing heart
The present mildly failing heart has not yet fallen into a typical Ca overload or paradox by the temporary Ca overloading intervention, and the recently developed formula of total Ca handling is found.
Myocardial mechanical restitution and potentiation partly underlie alternans decay of postextrasystolic potentiation: Simulation
It is concluded that myocardial mechanical restitution and potentiation may partly underlie the initial two alternating beats, the first beat being the most potentiated and the second beatbeing the most depressed, of alternans PESP decay in the canine heart.


Ryanodine decreases internal Ca2+ recirculation fraction of the canine heart as studied by postextrasystolic transient alternans.
Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis of O2 wasting of Ca2+ handling in the E-C coupling.
Effects of Ca2+ and epinephrine on Ca2+ recirculation fraction and total Ca2+ handling in canine left ventricles.
The results indicate that this new LV-level approach seems to better the understanding of the Ca2+ mass dynamics responsible for the mechanoenergetics enhanced by inotropic interventions.
Post-rest potentiation and its decay after inotropic interventions in isolated rat heart muscle.
In rat heart muscle, the inotropic interventions studied are not any more effective in augmenting force of contraction than prolonged stimulation intervals, suggesting that the distribution of Ca2+ into the sarcoplasmic reticulum is at a maximum during post-rest potentiation and that shifts in Ca 2+ distribution act as a limiting factor.
Postextrasystolic transient contractile alternans in canine hearts
The compensatory pause after either an atrial or ventricular extrasystole during occasional pacing failure seems essential for the postextrasystolic transient alternans of LV contractility in the type of canine heart preparation used consistently in mechanoenergetic studies.
Postextrasystolic Potentiation of the Isolated Canine Left Ventricle: Relationship to Mechanical Restitution
These phenomena could be quantitatively summarized by a single equation description of postextrasystolic contractile strength which involved monoexponential functions with one time constant which led to a simple interpretation of these phenomena in terms of currently proposed excitation-contraction coupling models of the heart.
Sinusoidal and exponential decays of postextrasystolic transient alternans in excised blood-perfused canine hearts.
This study suggests that myocardium has a mechanism to switch the postextrasystolic potentiation between the exponential and alternans decays depending on the first postext RAS interval.
Effect of adrenaline on cardiac force-interval relationship.
Test the hypothesis that adrenaline affects the force-interval processes in guinea pig papillary muscles and anaesthetised dogs and found that adrenaline exerts an inotropic effect by another mechanism that speeding up of mechanical restitution by adrenaline may be interpreted as reflecting the time course of reavailability of contractile activator.
Relationships between beat-to-beat interval and the strength of contraction in the healthy and diseased human heart.
A disturbance of excitation-contraction coupling mechanisms to explain the effects of recovery of left ventricular mechanical function and the degree of potentiation of the first postextrasystolic beat is postulated.
Characterisation of decay of frequency induced potentiation and post-extrasystolic potentiation.
The aim was to elucidate the processes underlying the beat by beat decay of frequency induced and post-extrasystolic potentiation in anaesthetised dogs with induced heart block and beta adrenergic blockade.
Epinephrine and calcium have similar oxygen costs of contractility
It is concluded that epinephrine and calcium have similar oxygen costs of contractility over a wide range of Emax despite their different pharmacological mechanisms of positive inotropism.