scholarly journals The Mechanochemistry of Cardiac Muscle

1967 ◽  
Vol 50 (4) ◽  
pp. 951-965 ◽  
Author(s):  
Peter E. Pool ◽  
Edmund H. Sonnenblick
Keyword(s):  
Cardiac Muscle ◽  
Adenosine Triphosphate ◽  
Papillary Muscle ◽  
Coupling Efficiency ◽  
Creatine Phosphate ◽  
Energy Utilization ◽  
Contractile Element ◽  
Cat Papillary Muscle ◽  
Net Production ◽  
Mechanochemical Coupling

The utilization of creatine phosphate (CP) and adenosine triphosphate (ATP) was studied in the iodoacetate (IAA) and nitrogen (N2)-treated cat papillary muscle. Under these conditions the net production of ATP does not occur, and the net utilization of ATP is reflected in a fall in CP concentration. The rate of energy utilization of the IAA-N2-treated cat papillary muscle resting without tension was 0.68 µmole CP/g/min. This rate was increased to 1.07 µmole/g/min when muscles were passively stretched with 2 g of tension. In a series of isometrically contracting muscles CP utilization was found to be proportional to the number of activations and the summated contractile element work. These rates of CP utilization were 0.083 µmole/g/activation and 0.0059 µmole/g-cm of work. The calculated mechanochemical coupling efficiency was 33%.

Enhanced contractility during relaxation of cat papillary muscle

1975 ◽  
Vol 228 (6) ◽  
pp. 1708-1716 ◽  
Author(s):  
BG Bass
Keyword(s):  
Papillary Muscle ◽  
Time Course ◽  
Isometric Tension ◽  
Contractile Element ◽  
Cat Papillary Muscle ◽  
Postextrasystolic Potentiation ◽  
Peak Tension ◽  
Time To Peak ◽  
In Series ◽  
Antecedent Control

Contractility during relaxation of isometric tension was studied in isolated, electrically driven cat papillary muscle by interpolation of test extrasystoles, all of whichpartially fused with their antecedent (control) contractions, were separated by computer from the fused contractions and then analyzed. The time course of the restitutionof contractility during relaxation was defined by plotting maximal positive dT/dt andtime-to-peak tension of the computer-separated extrasystole versus delay preceding the extrasystole. The dT/dt and time-to-peak tension, which steadily decline with progressive prematurity between contractions, both increase again during late relaxation, become progressively greater still earlier in relaxation, peak shortly after peak isometric tension, and then again decline. This phase of an apparently enhanced contractilityduring relaxation is depressed in low Ca'++ and is transmitted into the postextrasystolic period (in which it is superimposed on the usual postextrasystolic potentiation). The possible contributions of variations in series-elastic component and contractile-element lengths, actionpotential characteristics, and other factors on contractility during relaxation are discussed. It is suggested that enhanced contractility during relaxation may also be related in part to the decay of the intracellular free Ca'++ transient.

Nature of the Potentiating Substance in Cardiac Muscle

1958 ◽  
Vol 194 (3) ◽  
pp. 573-580 ◽  
Author(s):  
William J. Whalen ◽  
Noel Fishman ◽  
Rudolph Erickson
Keyword(s):  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Sympathetic Nerve ◽  
Posterior Wall ◽  
Atrial Appendage ◽  
Common Mechanism ◽  
Nerve Supply ◽  
Inotropic Action ◽  
Cat Papillary Muscle ◽  
Positive Inotropic Action

An extrasystole, rest, an increase in frequency, or above threshold stimulation with mass electrodes all potentiated the contractions of isolated cat papillary muscle and atrial appendage (but not strips from the posterior wall of the atria). The augmentation diminished or disappeared after the strips had been several days in the bath, after large doses of dibenamine, and after degeneration of the sympathetic nerve supply to the heart. In general, the augmentation phenomena were affected to about the same degree, which suggests a common mechanism. The results are consistent with our working hypothesis that all of the augmentation phenomena are due to intracardiac liberation of norepinephrine during each contraction, possibly from nerve endings. Evidence is presented that acetylcholine is released during activity in the cat papillary muscle as well as in the atria, and that the positive inotropic action of acetylcholine is probably due to the subsequent release of norepinephrine. Acetylcholine is apparently not a requisite for potentiation, however. The relative amounts of norepinephrine and acetylcholine liberated may determine whether augmentation or depression of contractility will be manifested.

Effect of hypoxia on mechanical properties of hyperthyroid cat papillary muscle

1979 ◽  
Vol 237 (3) ◽  
pp. H293-H298
Author(s):  
I. Palacios ◽  
K. Sagar ◽  
W. J. Powell
Keyword(s):  
Mechanical Properties ◽  
Right Ventricular ◽  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Similar Degree ◽  
Hypoxic Stress ◽  
Papillary Muscles ◽  
Tension Development ◽  
Cat Papillary Muscle ◽  
Myocardial Relaxation

It has been previously established that hyperthyroid myocardium exhibits increased performance under well-oxygenated conditions. To date, it is not known whether hyperthyroid cardiac muscle can maintain this increased performance during hypoxia. The responses of isolated right ventricular papillary muscles from hyperthyroid and euthyroid kittens to hypoxia were compared under isometric conditions at 31 degrees C. Under well-oxygenated conditions, the hyperthyroid cardiac muscle exhibited both an increased contractility and an accelerated rate of relaxation. A similar degree of acute hypoxic stress for 15 min resulted in a greater decrease in contractility in the hyperthyroid compared with the euthyroid papillary muscle as indicated by a greater fall in both peak tension development (2.2 +/- 0.25 from 4.2 +/- 0.2 vs. 0.9 +/- 0.15 from 3.2 +/- 0.4 g/mm2, P less than 0.01) and +dT/dt (12.9 +/- 2.3 from 25 +/- 3 vs. 4.0 +/- 0.6 from 14 +/- 1 g-s-1-mm-2, P less than 0.01). In addition, compared with the euthyroid data, hypoxia resulted in impaired myocardial relaxation in the hyperthyroid cardiac muscle. Thus, the hyperthyroid compared with the euthyroid papillary muscle exhibits both a greater decrease in contractility and an impairment of myocardial relaxation during hypoxia, indicating a greater susceptibility to a given hypoxic stress.

Characteristics of contraction in glycerinated uterine smooth muscle

1963 ◽  
Vol 204 (4) ◽  
pp. 739-742 ◽  
Author(s):  
Arthur H. Briggs
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Cardiac Muscle ◽  
Adenosine Triphosphate ◽  
Creatine Phosphate ◽  
Maximal Contraction ◽  
Uterine Smooth Muscle ◽  
Relaxing Factor ◽  
Uterine Muscle ◽  
Maximal Tension

Glycerinated guinea pig uterine fibers developed a maximal tension of 40 g/cm2 in castrated animals and 100 g/cm2 in animals pretreated with estrone or estrone-progesterone in the presence of both adenosine triphosphate (ATP), 5 mm, and Mg, 5 mm. In the absence of Mg, Ca had no effect on contraction induced by ATP (pH 6.5). However, following maximal contraction in ATP and Mg, 1 mm Ca induced a variable slight increase in tension in freshly extracted fibers (4 days-1 month) but not in fibers extracted for over 2 months. At a constant Mg level, 5 mm, the tension developed was a function of the ATP concentration from 0.1 mm to 5 mm (ADP and creatine phosphate had no effect). Above 5 mm, ATP resulted in relaxation which could be prevented by raising the Mg concentration. It was concluded that contraction in uterine muscle was basically similar to contraction in skeletal and cardiac muscle and that these uterine preparations may contain a labile relaxing factor(s) but did not contain ATP restituting systems.

scholarly journals Length-dependent calcium inotropism in cat papillary muscle.

1977 ◽  
Vol 40 (4) ◽  
pp. 366-371 ◽  
Author(s):  
L L Huntsman ◽  
D K Stewart
Keyword(s):  
Papillary Muscle ◽  
Cat Papillary Muscle

Effects of stretch on mechanical and electrical properties of cardiac muscle

1963 ◽  
Vol 204 (3) ◽  
pp. 433-438 ◽  
Author(s):  
Zia J. Penefsky ◽  
Brian F. Hoffman
Keyword(s):  
Relaxation Time ◽  
Electrical Properties ◽  
Papillary Muscle ◽  
Ground Squirrel ◽  
Action Potentials ◽  
Ventricular Wall ◽  
Contraction Time ◽  
Cat Papillary Muscle ◽  
Mechanical And Electrical Properties ◽  
Transmembrane Action Potentials

A comparative study was made of effects of stretch on cat papillary muscle and auricle strips, hamster ventricular wall, ground squirrel ventricular strip, chicken auricle and ventricle, terrapin auricle and ventricle strips, and carp ventricle. In all species mild stretch increased contractile tension, excessive stretch decreased it, and velocity of conduction was constant with mild stretch but decreased with excessive stretch. In homeotherms under mild stretch, contraction time was unchanged and increased contractile tension was accompanied by increase in velocity of contraction. Under excessive stretch contraction time increased despite decreasing contractile tension. In poikilotherms contraction time and contractile tension were increased by mild stretch. Contraction time decreased with excessive stretch. Stretch increased relaxation time in all species. The evidence suggests that decrease in contractile tension with stretch is related, at least in the initial phases, to a change in excitability and conduction. In all species mild stretch was without effect on transmembrane action potentials, whereas at excessive stretch resting potentials and overshoot declined and rise time of the action potential was greatly increased. At excessive stretch surface-recorded potentials exhibited polyphasic deflections. All observed responses to stretch were reversible. Immediately after stretch the fibers were slightly elongated but developed a higher maximal contractile tension, and contraction time also was slightly increased.

Effects of rate and rhythm on contraction of rat papillary muscle

1959 ◽  
Vol 197 (6) ◽  
pp. 1199-1204 ◽  
Author(s):  
Brian F. Hoffman ◽  
John J. Kelly
Keyword(s):  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Ionic Composition ◽  
Force Frequency ◽  
Progressive Decrease ◽  
Plasma Epinephrine ◽  
Perfusion Medium ◽  
Frequency Relationship ◽  
Rat Papillary Muscle ◽  
Isolated Rat

The unusual relationship between frequency of contraction and tension developed by the isolated rat papillary muscle has been studied in detail. The progressive decrease in tension with increasing rate is unrelated to the size or weight of the muscle and is not changed by alterations in the ionic composition of the perfusion medium. The force-frequency relationship is also unchanged by addition of plasma, epinephrine or digitalis to the perfusion medium. Rat papillary muscle is similar to other preparations of cardiac muscle with respect to recovery of contractility and the development of rest contractions and postextrasystolic potentiation.

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