The role of troponin C in the length dependence of Ca(2+)‐sensitive force of mammalian skeletal and cardiac muscles.

Gulati, Jagdish; Sonnenblick, Edmund H.; Babu, A.

doi:10.1113/jphysiol.1991.sp018753

Cited by 68 publications

(71 citation statements)

References 52 publications

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“…Similar findings were made in numerous studies on warm-blooded animal and human myocardium [9,[16][17][18][19][20][21][22][23][24]. The preload-induced interplay between cytosolic calcium and force development is thought to be indirect and most likely involves cooperative effects of association/dissociation of Ca-TnC [2,4,6,7,30,31].…”

Section: Discussionsupporting

confidence: 63%

“…The primary mechanism of force-length relation is the preload-dependence of sarcomere filament overlap which dictates the total number of sites available for interaction of myosin filament with actin [2][3][4]. This indirectly results in augmentation of troponin C (TnC) affinity to Ca 2+ in mammalians [5][6][7]. Preload-dependent changes in calcium handling in cardiomyocytes are more complex and controversial.…”

Section: Introductionmentioning

confidence: 99%

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Preload-induced changes in isometric tension and [Ca2+]i in rat myocardium

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Protsenko

2011

Open Life Sciences

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Preload-induced changes of active tension and [Ca2+]i are “dissociated” in mammalian myocardium. This study aimed to describe the distinct effects of preload at low and physiological [Ca2+]o. Rat RV papillary muscles were studied in isometric conditions at 25‡C and 0.33 Hz at 1 mM (hypo-Ca group) and 2.5 mM [Ca2+]o (normal-Ca group). [Ca2+]i was monitored with fura-2/AM. Increase of preload caused a rise of active tension in hypo-Ca and normal-Ca groups whereas peak fluorescence rose significantly only at low [Ca2+]o. End-diastolic tension, end-diastolic level of fluorescence, time-to-peak tension, but not time-to-peak of Ca2+ transient, progressively increased with preload. Mechanical relaxation decelerated with preload while Ca2+ transient decay time decreased in the initial phase and increased in the late phase, resulting in a prominent “bump” configuration. The “bump” was assessed as a ratio of its area to the fluorescence trace area. It was a new finding that the preload-induced rise of this ratio was twice as large in hypo-Ca. Our results indicate that preload-induced changes in active tension and [Ca2+]i are “dissociated” in rat myocardium, with relatively higher expression at low [Ca2+]o. Ca-dependence of Ca-TnC association/dissociation kinetics is thought to be a main contributor to these preload-induced effects.

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Section: Discussionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Preload-induced changes in isometric tension and [Ca2+]i in rat myocardium

Lookin

Protsenko

2011

Open Life Sciences

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“…Mechanical performance of the myocardium. Along the ascending limb of the cardiac length-tension curve, developed tension is length dependent and this property is related to the calcium activation of myofilaments mediated by the troponintropomyosin protein regulatory complex (20,21). The overlapping of thin and thick filaments is unchanged in the positive portion of the Frank-Starling relation (22), and the changes in resting length and force development are related to the extent of calcium myofilament interaction (22,23).…”

Section: Discussionmentioning

confidence: 99%

Stretch-induced programmed myocyte cell death.

Cheng

Li²,

Kajstura³

et al. 1995

J. Clin. Invest.

593

313

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To determine the effects of loading on active and passive tensions, programmed cell death, superoxide anion formation, the expression of Fas on myocytes, and side-to-side slippage of myocytes, papillary muscles were exposed to 7-8 and 50 mN/mm2 and these parameters were measured over a 3-h period. Overstretching produced a 21-and a 2.4-fold increase in apoptotic myocyte and nonmyocyte cell death, respectively. Concurrently, the generation of reactive oxygen species increased 2.4-fold and the number of myocytes labeled by Fas protein 21-fold. Moreover, a 15% decrease in the number of myocytes included in the thickness of the papillary muscle was found in combination with a 7% decrease in sarcomere length and the inability of muscles to maintain stable levels of passive and active tensions. The addition of the NO-releasing drug, C87-3754, prevented superoxide anion formation, programmed cell death, and the alterations in active and passive tensions with time of overloaded papillary muscles. In conclusion, overstretching appears to be coupled with oxidant stress, expression of Fas, programmed cell death, architectural rearrangement of myocytes, and impairment in force development of the myocardium. (J. Clin. Invest. 1995. 96:2247-2259

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“…To answer this question, different lines of investigation and hypotheses are presently under investigation. Some authors suggest that TnC itself might be the sensor of changes in muscle length [20][21][22] . This hypothesis is based on molecular differences between TnC of cardiac and skeletal muscle, which might be associated with the difference in the force-length relationship in both muscles.…”

Section: The Degree Of Activation Of Cardiac Muscle Depends On Musclementioning

confidence: 99%

The degree of activation of cardiac muscle depends on muscle length

Rassier¹

2000

Arq. Bras. Cardiol.

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The Frank-Starling mechanism of the heart 1-3 can be described as the relationship between force and length of cardiac muscle. With the advent of the cross bridge theory of muscle contraction 4,5 and Gordon and collaborator's classical study 6 describing the fitting of this theory to the force-length relationship in skeletal muscle, several investigators started to study this relationship in cardiac muscle.The force-length relation in cardiac muscle is observed in a small variety of sarcomere lengths, between approximately 1.8 µm and 2.3 µm. This region corresponds to the ascending limb of the force-length relation of skeletal-muscle 6 . The force levels of the myocardium vary from zero at 1.8 µm to maximal force values at 2.3 µm. This large variation in force results in a very sleep force-length relation, especially when compared with this relation in skeletal muscle ( fig. 1). To get an idea, when the tension developed by the myocardium at different sarcomere lengths is normalized in relation to its maximal force (F max ) at the point where maximal length (L max ) occurs, the developed tension is approximately 10-15% when the myocardium is measured at 80% L max . Yet in skeletal muscle, normalized force is approximately 80-85% of F max 7 under the same conditions ( fig.1).This difference between skeletal and cardiac muscle shows that the force-length relationship in the myocardium are not a simple function of the degree of superposition of actin and myosin filaments. Because their lengths are similar in both muscles, other factors must be involved in the muscle force-length relationship. During recent years, this difference has been attributed to the dependence of muscle activation on sarcomere length 8 .Muscle activation has been used collectively in the literature to refer to various processes able to initiate muscle contraction, modifying the muscle state from "inactive" to "active". Thus, muscle activation has been associated with the frequency of muscle stimulation or membrane action potentials with intracellular Ca 2+ concentration [Ca 2+ ] i , or the occupation of the protein troponin C (TnC) by Ca 2+ . In this article, the term muscle contraction will be utilized to describe the proportion of TnC associated with Ca 2+ . The association TnC/Ca 2+ represents a fundamental event in muscle contraction; therefore, the sensitivity of TnC to Ca 2+ will be discussed in greater detail. This choice, furthermore, comes from studies shewing that myocardial force changes due to muscle length are unrelated to [Ca 2+ ] i 9,10 . The present article contains a review of studies related to the dependence of force and, more importantly, of the process of myocardial muscle activation on muscle length. In particular, the article intends to investigate mechanisms responsible for the dependence of the sensitivity of filaments to Ca 2+ on muscle length, as proposed in the literature.Dependence of the sensitivity of filaments to Ca 2+ on muscle length -Evidence that the activation of the myocardium is dependent on muscle lengt...

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The role of troponin C in the length dependence of Ca(2+)‐sensitive force of mammalian skeletal and cardiac muscles.

Cited by 68 publications

References 52 publications

Preload-induced changes in isometric tension and [Ca2+]i in rat myocardium

Preload-induced changes in isometric tension and [Ca2+]i in rat myocardium

Stretch-induced programmed myocyte cell death.

The degree of activation of cardiac muscle depends on muscle length

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