Quantitative Studies on the Ultrastructural Differentiation and Growth of Mammalian Cardiac Muscle Cells

Gotoh, Tadashi

doi:10.1159/000145687

Cited by 33 publications

(9 citation statements)

References 9 publications

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“…However, much less is known about the expression and function of sarcolemmal tubules in atrial cells. Although it is commonly cited that mammalian atrial myocytes do not possess T-tubules [5,9,26], it has been suggested that these cells possess a rudimentary transverse-axial tubular system [21][22][23]25,33]. Results obtained from immunostaining (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…All experiments were performed at room temperature (20)(21)(22) • C), since cell viability and dye loading is prolonged at this temperature. Prior to starting experiments, all cells were paced for a brief period to establish a steady-state Ca 2+ response.…”

Section: Confocal and Photometry Imagingmentioning

confidence: 99%

“…Although there is wide agreement that adult atrial myocytes do not possess the extensive T-tubule network found in their ventricular counterparts, it has been proposed that they express a more rudimentary transverse-axial tubular network [21][22][23][24][25]. It has been presumed that this tubular system would influence atrial Ca 2+ signalling and excitation-contraction coupling [25], but there is limited functional data in support of this notion.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation–contraction coupling and inotropic stimulation

et al. 2010

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a b s t r a c t Narrow, tubular, inward projections of the sarcolemma ('T-tubules') are an established feature of adult mammalian ventricular myocytes that enables them to generate the whole-cell Ca 2+ transients and produce coordinated contraction. Loss of T-tubules can occur during ageing and under pathological conditions, leading to altered cardiac excitation-contraction coupling. In contrast to adult ventricular cells, atrial myocytes do not generally express an extensive T-tubule system at any stage of development, and therefore rely on Ca 2+ channels around their periphery for the induction of Ca 2+ signalling and excitation-contraction coupling. Consequently, the characteristics of systolic Ca 2+ signals in adult ventricular and atrial myocytes are temporally and spatially distinct. However, although atrial myocytes do not have the same regularly spaced convoluted T-tubule structures as adult ventricular cells, it has been suggested that a proportion of adult atrial cells have a more rudimentary tubule system. We examined the structure and function of these atrial tubules, and explored their impact on the initiation and recovery of Ca 2+ signalling in electrically paced myocytes. The atrial responses were compared to those in adult ventricular cells that had intact T-tubules, or that had been chemically detubulated. We found that tubular structures were present in a significant minority of adult atrial myocytes, and were unlike the T-tubules in adult ventricular cells. In those cells where they were present, the atrial tubules significantly altered the on-set, amplitude, homogeneity and recovery of Ca 2+ transients. The properties of adult atrial myocyte Ca 2+ signals were different from those in adult ventricular cells, whether intact or detubulated. Excitation-contraction coupling in detubulated adult ventricular myocytes, therefore, does not approximate to atrial signalling, even though Ca 2+ signals are initiated in the periphery of the cells in both of these situations. Furthermore, inotropic responses to endothelin-1 were entirely dependent on T-tubules in adult ventricular myocytes, but not in atrial cells. Our data reveal that that the T-tubules in atrial cells impart significant functional properties, but loss of these tubular membranes does not affect Ca 2+ signalling as dramatically as detubulation in ventricular myocytes.

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Section: Discussionmentioning

confidence: 99%

Section: Confocal and Photometry Imagingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation–contraction coupling and inotropic stimulation

et al. 2010

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“…However, a few studies have demonstrated a component of fast Ca 2+ release within central regions of atrial cells (Kirk et al, 2003;Woo et al, 2002). As mentioned above, some atrial myocytes have a rudimentary T-tubule system (Ayettey and Navaratnam, 1978;Gotoh, 1983;Tidball et al, 1991), and this may be the basis for some rapid central Ca 2+ responses. In atrial cells that have T-tubules, electrically evoked Ca 2+ signals originate simultaneously at multiple independent locations within the cells (Kirk et al, 2003).…”

Section: Rapid Central Camentioning

confidence: 99%

“…2Biii; the Na + /Ca 2+ exchanger immunostaining is around the outside of the cell only), although some atrial cells possess a more rudimentary transverse-axial tubular network (Ayettey and Navaratnam, 1978;Brette and Orchard, 2003;Gotoh, 1983;Tidball et al, 1991). In place of the T-tubules, atrial cells have prominent SR elements, which have been described as 'Z-tubules' (Fig.…”

Section: Atrial Myocyte Ec Coupling Unlike Ventricular Myocytes Atrimentioning

confidence: 99%

Calcium signalling during excitation-contraction coupling in mammalian atrial myocytes

Bootman

Higazi

Coombes

et al. 2006

Journal of Cell Science

137

107

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Physiological role of atrial myocytesThe heart undergoes a cycle of events that cause blood to be propelled to the lungs and the body. These events can be divided into two stages: diastole and systole. During the diastolic stage, the atrial and ventricular myocytes are relaxed. Systole refers to the period of contraction and consequent ejection of blood from the ventricles to the pulmonary artery or aorta. The cardiac cycle is initiated by the sinoatrial nodea group of specialised non-contractile cardiac myocytes positioned in the wall of the right atrium. All of the cells in the heart have an intrinsic ability generate action potentials (electrical impulses). However, the sinoatrial node acts as the primary pacemaker because its cells naturally discharge at a high rate, and so override the other potential pacemaking sites. Hormonal modulation of the sinoatrial node is one of the principal mechanisms for altering the frequency of the heartbeat. From the sinoatrial node, the action potential spreads over the atria causing them to contract and push blood into the ventricles. As the wave of depolarisation sweeps across the heart, it reaches the atrioventricular node, which filters and relays the signal to the ventricles via specialised conduction tissue including the Purkinje fibres. The atrial chambers contract and relax before the ventricular systole, and their activation is evident as separate electrical activity in an electrocardiogram. The time course of contraction is marginally shorter in atria compared to ventricles. Both cell types reach peak contraction within a few tens of milliseconds (Luss et al., 1999).The ventricles contract more forcefully than the atrial chambers and are predominantly responsible for forcing blood out of the heart. However, atria can play a significant role in altering the amount of blood that loads into the ventricles before to systole. When a person is at rest, the contribution of atria to the filling of ventricles with blood is relatively low. The majority (~90%) of ventricular refilling occurs as a consequence of the venous pressure of blood returning to the heart. However, if the heart rate increases, such as during exercise or stress, then atrial contraction can account for ~20-30% of the volume of blood in the ventricles. This contribution to ventricular refilling is known as 'atrial kick' (Lo et al., 1999). Under some pathological conditions (such as mitral valve stenosis) and during ageing, the dependence on atrial kick can be critical (Nicod et al., 1986).A common form of cardiac dysrhythmia known as 'atrial fibrillation' occurs when electrical impulses do not solely arise from the sinoatrial node, but instead spontaneously occur with high frequency from sites around the atria (~350 discharges per minute, compared with the normal sinoatrial rhythm of 60-80 beats per minute). The rapid and irregular electrical discharges during atrial fibrillation cause the atria to quiver and thereby

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The transverse‐axial tubular system (tats) of mouse myocardium: Its morphology in the developing and adult animal

1984

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Invaginations of the sarcolemma that generate the transverse-axial tubular system (TATS) of the ventricular myocardial cells have begun to develop in the mouse by the time of birth. The formation of the TATS appears to be derived from the repetitive generation of caveolae, which forms "beaded tubules". Beaded tubules are retained in the adult, in which they frequently present a spiraled topography. Development of the TATS progresses so rapidly that complex systems are already present in the cardiac muscle cells of young mice; by 10-14 days of age, the ultrastructure is essentially identical to that of the adult. The mouse myocardial TATS is composed of anastomosed elements that are directed transversely and axially (longitudinally). Many tubules have an oblique orientation, however, and most elements of the TATS are highly pleiomorphic. In this respect the TATS of the mouse heart is relatively primitive in appearance in comparison with the more ordered TATS latticeworks typical of the ventricular cells of other mammals. Stereological analysis of the mouse TATS indicates that the volume fraction (VV) and surface density (SV) are considerably greater than previously reported (3.24% and 0.5028 micron-1, respectively). The most complex ramifications of the TATS are embodied in the subsarcolemmal caveolar system and the deeper tubulovesicular "labyrinths", both of which can be found in early postnatal and adult ventricular cells. In atrial cells, TATS development is initiated several days later than in the ventricular cells. The TATS of adult atrial myocardial cells is less prominent than the ventricular TATS and consists largely of axial elements; the incidence of the TATS, furthermore, is more pronounced in the left than in the right atrium.

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Quantitative Studies on the Ultrastructural Differentiation and Growth of Mammalian Cardiac Muscle Cells

Cited by 33 publications

References 9 publications

Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation–contraction coupling and inotropic stimulation

Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation–contraction coupling and inotropic stimulation

Calcium signalling during excitation-contraction coupling in mammalian atrial myocytes

The transverse‐axial tubular system (tats) of mouse myocardium: Its morphology in the developing and adult animal

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