Rapid Relengthening in Isolated Cardiac Cells and the Origin of Diastolic Recoil

Krueger, John W.

doi:10.1007/978-4-431-67957-8_3

Cited by 4 publications

(5 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ␣ 1 -adrenoceptor stimulation shifts the trajectory, in particular the re-lengthening phase, to the left, which suggests an increase in Ca 2ϩ responsiveness. However, the re-lengthening phase of the trajectory, particularly in unloaded shortening, is significantly influenced by repulsion (restoring) force of the elastic components including cytoskeleton, connectin, and other factors rather than the active cross-bridges [8]. Therefore, the re-lengthening phase of the trajectory, in particular the later phase, does not directly reflect the Ca 2ϩ responsiveness measured using the pCa-ten- Key words: Ca 2ϩ sensitivity, phenylephrine, Na/H exchange, intracellular pH, protein kinase C (PKC).…”

mentioning

confidence: 99%

The Mechanism of Increasing Ca2+ Responsiveness by .ALPHA.1-Adrenoceptor Stimulation in Rat Ventricular Myocytes.

Kusakari

Hongo²,

Kikuchi³

et al. 2002

JJP

View full text Add to dashboard Cite

It has been reported that ␣ 1 -adrenoceptor stimulation increases contraction with or without a significant change in the peak of Ca 2ϩ transient, and an increase in the Ca 2ϩ responsiveness of the contractile element is considered to be one of the possible mechanisms [1,2]. The increase in the Ca 2ϩ responsiveness of the contractile element by ␣ 1 -adrenoceptor stimulation is explained by intracellular alkalinization or phosphorylation of the contractile elements or both, but the relative contribution of the two mechanisms is still unclear owing to controversy in experimental results [3][4][5][6].For the assessment of Ca 2ϩ responsiveness, a phase-plane loop (trajectory), obtained by measuring the relation between the intracellular Ca 2ϩ transient and cell shortening in a single isolated myocyte loaded with a fluorescent dye, has been widely used [7]. The ␣ 1 -adrenoceptor stimulation shifts the trajectory, in particular the re-lengthening phase, to the left, which suggests an increase in Ca 2ϩ responsiveness. However, the re-lengthening phase of the trajectory, particularly in unloaded shortening, is significantly influenced by repulsion (restoring) force of the elastic components including cytoskeleton, connectin, and other factors rather than the active cross-bridges [8]. Therefore, the re-lengthening phase of the trajectory, in particular the later phase, does not directly reflect the Ca 2ϩ responsiveness measured using the pCa-ten- Key words: Ca 2ϩ sensitivity, phenylephrine, Na/H exchange, intracellular pH, protein kinase C (PKC). Abstract:We investigated the mechanism of ␣ 1 -adrenoceptor stimulation on the myofibrillar Ca 2ϩ responsiveness at steady-state in intact rat ventricular myocytes. We produced tetanus, and an instantaneous plot of [Ca 2ϩ ] i vs. cell length (Ca-L trajectory) was constructed to estimate the Ca 2ϩ responsiveness. An ␣ 1 -agonist, phenylephrine, dose-dependently shifted the Ca-L trajectory to the left, corresponding to sensitization of the myofilaments. An ␣ 1 -antagonist, prazosin, and inhibition of the Na/H exchange by ethylisopropylamiloride (EIPA) completely reversed the phenylephrine-induced shift. Phenylephrine increased pH i (⌬pH i ϭϩ0.1), which was reversed by prazosin and EIPA. Chelerythrine, an inhibitor of protein kinase C (PKC), completely blocked the effects of phenylephrine on Ca 2ϩ responsiveness and pH i . When pH i was increased (⌬pH i ϭ ϩ0.1) without phenylephrine by changing pH o , the Ca-L trajectory was shifted to the same extent as that observed with phenylephrine. We conclude that ␣ 1 -adrenoceptor stimulation activates Na/H exchange through a PKC-mediated pathway and that an increase in pH i is mainly responsible for the increase in Ca 2ϩ responsiveness.

show abstract

mentioning

confidence: 99%

The Mechanism of Increasing Ca2+ Responsiveness by .ALPHA.1-Adrenoceptor Stimulation in Rat Ventricular Myocytes.

Kusakari

Hongo²,

Kikuchi³

et al. 2002

JJP

View full text Add to dashboard Cite

show abstract

“…Observation of individual striations in asynchronously contracting heart cells have found that the velocities of shortening and relengthening appear constant (16), a behavior that would result in a 'triangular' pattern of shortening and relengthening. We have never observed this pattern of shortening in synchronized contractions (8,10,13,14). However, the reversibility in the dynamics of the sarcomere in contiguous contractions show that asynchrony could make the velocity of both shortening or relengthening appear more constant.…”

Section: Asynchronous Sarcomere Mechanicsmentioning

confidence: 77%

“…Unattached cells produce little force, but early relengthening of the fibers of the heart can occur at comparably low forces. A very simple model of the ventricle indicates that a force of only 0.5 mN/mm2 would be sufficient to create negative intraventricular pressures of 10 mmHg (8).…”

Section: Implications For the Involvement Of The Cell In Diastolic Rementioning

confidence: 99%

“…The isolated cardiac cell relengthens vigorously (8,13,14), and a steady restoring force can be measured in the isolated cardiac myofibril (4) or cell (7) that has been shortened to below its rest length. The contribution of the cellular relengthening force to the restoring force in isolated heart muscle is unclear, however, largely because the former has not been measured in physiologically intact cells.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Nature of motions between sarcomeres in asynchronously contracting cardiac muscle cells

Krueger

Denton

Siciliano

1992

Biophysical Journal

View full text Add to dashboard Cite

We observed the asynchronized motions that occur between the sarcomeres during spontaneous contractions to study the mechanical nature of the intact cardiac muscle cell (guinea pig, rat). The cell's striated image is detected by a photodiode array, and sarcomere length is measured very precisely 526/s in two separate, selected fixed regions of the image from the localized frequency of the array's video signal (Krueger and Denton, 1992, Biophys. J., 61:129-144, second of two companion manuscripts). An extension of this approach is described here in which the spatial variation of sarcomere length is visualized by scanned sampling, i.e., displacing the first window along the length of the cell, and nonuniform strain is deduced from the histograms of sarcomere length. The nature of asynchronous motion that was obtained from both fixed sampling of the sarcomere's dynamics and by scanned sampling of sarcomere length was consistent. In spontaneously active cells, sarcomeres lengthen approximately 0.1 micron beyond their rest length before the arrival of the propagated wave of contraction. Such prelengthening extends in a nonuniform fashion for approximately 10 to 15 microns in the unattached cell. Shortening and lengthening motions, being in proportion for both large and small displacements, are well coupled. Lifting the cell from the substrate showed that the force that sustains prelengthening arises within the cell. Differences in the sarcomere's dynamics in synchronous and asynchronous contractions corroborate that asynchrony imposes an additional internal restoring force. The extra force estimated to account for prelengthening (0.5-0.7 mN/mm2) has little effect on the velocity of shortening, and so the true intracellular restoring force must be correspondingly larger. The intracellular restoring force may contribute significantly to the rapid 'diastolic' recoil of the heart muscle at short sarcomere lengths.

show abstract

“…Likewise, major advances in underrestoring forces in the isolated myocyte may be more in 21 restoring diastolic cell length than in influencing the standing Ca oscillations and cellular mechanisms of length-tension relation [24], since the measured restoring dysrrhythmia have come from studies in single cells. 21 force in relaxing myocytes has been estimated to be only Simultaneous measurements of cytosolic Ca and cell of the order of |4% of the total active force [73,74]. In shortening have also provided significant information fact, the quiescent unloaded myocyte may be uniquely regarding the inter-relationship between these variables, sensitive in indexing small alterations in ''passive'' propespecially with respect to a variety of inotropic interven-21 erties, which are reflected in Ca -independent changes in tions.…”

Section: The Isolated Heartmentioning

confidence: 99%

Physio-pharmacological evaluation of myocardial performance: an integrative approach

Shah

Sollott

Lakatta

1998

Cardiovascular Research

View full text Add to dashboard Cite

sion have altered out of all recognition compared to the Despite major advances in the understanding of carapproaches of 40-50 years ago. diovascular physiology and pathophysiology and the deWithin this context, the questions that are considered in velopment of new therapies in the 20th century, carthis article are: How should myocardial performance best diovascular disease is projected to become the leading be assessed? What are the advantages and disadvantages of overall cause of mortality worldwide within the next currently used methodologies? How far can and should couple of decades [1]. In the western world, an increasing reductionism be pursued? What is the relevance of animal proportion of older people in the population accounts for models? The implicit pre-requisite in answering these the lack of reduction in the absolute number of carquestions is that information obtained using any particular diovascular deaths, whereas in developing countries, part approach should, ultimately, be of some relevance to of the reason is the adoption of ''western'' lifestyles and human cardiovascular function or dysfunction. their accompanying coronary risk factors as socioeconomic Although we focus in this counterpoint article on the in status gradually improves and mortality from infectious vitro assessment of myocardial contractile behaviour, it is and other diseases of early life decrease. There remain clear that many other aspects of cardiac function as well as significant gaps in our understanding of many aspects of that of other organs will be relevant to the understanding cardiovascular diseases and the contribution of risk factors of cardiovascular disorders. Within the heart, coronary such as smoking, hypercholesterolaemia, hypertension and vascular function, endothelial function, the influence of diabetes. In addition, increasing numbers of patients who blood cells, neural control, the release of circulating survive ischaemic cardiac disorders develop heart failure.hormones, such as natriuretic peptides, locally active Traditionally, the focus of research into cardiovascular paracrine and autocrine substances, and the properties of disease was the heart and myocardium, but in the last the extracellular matrix may all be relevant to contractile several decades, the importance of the vasculature and of function as well as other aspects, such as energetics, other body systems has been better appreciated. The field growth, hypertrophy and so on. With respect to the of vascular biology has blossomed. Traditionally, invescontractile process itself, and its regulation, a full undertigators focused on mechanical function. However, in the standing requires information about excitation-contraction last several decades, investigative approaches have coupling, signal transduction, myofilament mechanisms, broadened dramatically, ranging from molecular and celenergetics and molecular mechanisms, to name but a few lular biology and physiology, to in vitro and in vivo relevant aspects. studies in animal models of disease, to st...

show abstract

Rapid Relengthening in Isolated Cardiac Cells and the Origin of Diastolic Recoil

Cited by 4 publications

References 17 publications

The Mechanism of Increasing Ca2+ Responsiveness by .ALPHA.1-Adrenoceptor Stimulation in Rat Ventricular Myocytes.

The Mechanism of Increasing Ca2+ Responsiveness by .ALPHA.1-Adrenoceptor Stimulation in Rat Ventricular Myocytes.

Nature of motions between sarcomeres in asynchronously contracting cardiac muscle cells

Physio-pharmacological evaluation of myocardial performance: an integrative approach

Contact Info

Product

Resources

About