Role of contraction in the structure and growth of neonatal rat cardiocytes

Marino, Thomas A.; Kuseryk, L.; Lauva, Ines K.

doi:10.1152/ajpheart.1987.253.6.h1391

Cited by 21 publications

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“…Early studies showed that attachment of neonatal or adult cardiac myocytes to a collagen coated, rigid substrate stimulated cellular growth in culture even in the absence of 5. The ECM-integrin-cytoskeletal complex additional mechanical load [38,39]. In retrospect, these participates in cell signaling in vivo findings were consistent with growth-promoting signals arising from focal adhesions as the isolated, quiescent cells Remarkably little is known about the role of costameres attached and spread in culture, but the activation of cell in regulating growth and function of cardiomyocytes in signaling was not explored.…”

Section: Introductionmentioning

confidence: 80%

Specialization at the Z line of cardiac myocytes

Borg

Goldsmith

Price

et al. 2000

Cardiovascular Research

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Introductioncytoskeletal connections for cell-ECM contacts. The formation of these regions appears to be a coordinated The organization of any differentiated cell is not random expression of ECM components, cell surface receptors, and but is the result of a dynamic integration of extracellular signaling proteins [1][2][3][4][5]. The localization of fibronectin, and intracellular signals. During the development of the integrins, cadherins, and kinase / phosphotase complexes, heart, cardiac myocytes are round shaped cells that difwhich are all important to myofibrillogenesis, appear as ferentiate into a rod-shaped phenotype. During the differfocal patches on the myocyte surface (Fig. 2). Interaction ent stages of commitment and morphogenesis, the myocyte with the ECM occurs throughout development; however, organizes its internal structure by undergoing myofibrilthe specialization to define the Z bands appears to be logenesis. This process results in the precise arrangement coordinated with myofibrillogenesis and the deposition of of contractile elements, supporting cytoskeleton, and endocollagen. Fibroblasts appear to secrete collagen that is then plasmic reticulum. Within the sarcolemma, specialized attached to regions on the myocyte where the Z bands are regions are defined for attachment to components of the forming internally [6]. Myofibrillogenesis appears to start extracellular matrix (ECM). This specialized site of the in vivo near the internal margin of the sarcolemma [7,8]. sarcolemma consists of the ECM-Receptor-Cytoskeleton This observation would be consistent with the presence of complex (Fig. 1). These sites will integrate attachment to specific receptors in the sarcolemma prior to myofibrilthe ECM and the series of proteins necessary for the logenesis necessary for the attachment of the myofibril to chemical and mechanical transmission of information. In the Z band at the same site where collagen is attaching on this review, we will describe the evidence that indicates the outside. These morphological data are consistent with there is a specialization of the sarcolemma at the Z line for the presence of the integrin receptors within the membrane the clustering of various receptors for the ECM as well as at this time [9]. The formation of the collagenous 'struts' the cytoskeleton.begins with attachment of a few collagen fibers which appear to increase in number ( Fig. 2A). Associated with these attached fibers on the extracellular side are proteo-2. Development of specialized regions of the glycans and glycoproteins [10]. What is not known is how sarcolemma the fibroblast 'finds' the myocyte to secrete the collagen at such a precise location. The presence of collagen receptors During development of the embryonic heart, two (integrins) on the myocyte at these sites indicates that these specialized regions of the sarcolemma develop: (1) intercareceptors may play a role in directing collagen strut lated disks for cell-cell interaction and (2) ECM-integrinformation [11] (Fig. 2B). Collagen struts do not ap...

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Section: Introductionmentioning

confidence: 80%

Specialization at the Z line of cardiac myocytes

Borg

Goldsmith

Price

et al. 2000

Cardiovascular Research

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“…Growth of neonatal cardiac myocytes in culture is facilitated by contraction and attachment to a substrate. 3435 Marino and colleagues 34 reported that neonatal myocytes cultured in serum-free medium failed to grow when either attachment or contraction was prevented. McDermott and Morgan 35 demonstrated that contractile activity of cultured neonatal myocytes increased the capacity for protein synthesis via an increase in RNA synthesis, supporting a role for contractile activity in myocyte growth.…”

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Genetic, neurohumoral, and hemodynamic influences on spontaneously hypertensive rat heart development in oculo.

Tucker

1990

Hypertension

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To distinguish among genetic, neurohumoral, and hemodynamic explanations for structural and functional differences in the hearts of young spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) control rats, embryonic SHR and WKY rat heart tissue was cultured in the anterior eye chamber of adult SHR and WKY rats. In study 1, atria from E-L2 WKY rat embryos grafted into anterior eye chambers of either SHR or WKY host rats achieved a larger size than did SHR grafts by 8 weeks in oculo (2.98 ±0. 75 ; WKY rat hearts, 1.75±0J9 vs. 2 J 9 ± 0 J 2 mm 1 ). Ventricle grafts from SHR embryos into SHR host rats beat more rapidly (165 ±19 beats/min) during weekly measurements than either WKY rat ventricles (92±9 beats/min in SHR hosts and 99±9 beats/min in WKY host rats) or SHR ventricles grafted into WKY host rats (109±7 beats/min, p<0Ml).In study 3, atria from E-13 SHR and WKY rat embryos were grafted into sympathectomized and intact eye chambers of SHR or WKY host rats. Sympathectomy of the eye chamber compromised growth of grafts into WKY host rats (1.54±0.24 vs. 0.90±0.14 mm 2 ) but not SHR hosts (1.54±0.25 vs. 1.73±0.24 mm 2 ). Grafts into sympathectomized eye chambers of WKY host rats beat more slowly than grafts into eye chambers with sympathetic innervatlon intact (282±14 vs. 202±14 beats/min); sympathectomy did not alter beating rate of grafts in SHR hosts (266±14 vs. 255±18 beats/min). These results suggest that the growth and beating rate of SHR atrial grafts may be less sensitive to sympathetic innervation than WKY rat atrial grafts. In these studies, SHR grafts did not grow larger than WKY heart grafts and did not show an increased intrinsic beating rate, suggesting that the cardiac hypertrophy and increased intrinsic beating rate observed in intact SHR are unlikely to result from direct genetic programming. (Hypertension 1990;15:247-256) T he predisposition to development of hypertension is manifested very early in rats of the spontaneously hypertensive rat (SHR) strain. Structural alterations in the heart and vasculature observed in young SHR may contribute to or may result from the increase in blood pressure. Blood pressure in SHR has been measured as early as 20 days of gestation and found to be elevated compared Because of technical difficulties, it is not known how early blood pressure in the SHR fetus becomes elevated relative to WKY rat controls. EcclestonJoyner and Gray 7 found both structural alterations in the vasculature and evidence of increased ventricular mass relative to body weight at 17 days of gestation in SHR compared with WKY rats. Possible explanations of these early structural alterations in the heart and vasculature include: 1) adaptation to the increased blood pressure of SHR, 2) altered development in response to neural or humoral signals, and 3) genetically programmed hypertrophy. 8 In hypertensive animals, hypertrophy of the heart and vascular walls results from increased pressure 9 and from non-pressure-related mechanisms.

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“…12 In contrast, recent studies have demonstrated that regular rates of contraction in low KC1 medium stimulate growth of adherent neonatal myocytes in culture. 13 In general, the specific mechanisms by which protein synthesis is regulated at either the transcriptional or translational level have not been defined for any growth stimulus.…”

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Contraction modulates the capacity for protein synthesis during growth of neonatal heart cells in culture.

McDermott

Morgan

1989

Circulation Research

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Neonatal ventricular myocytes that were incubated in a well-defined serum-free medium containing 50 mM KCl did not contract and maintained stable cell size, as assessed by the protein/DNA ratio. The present study utilized KCl-arrested cells to examine the effect of constant rates of synchronous contraction in normal [K+]o (4 mM) as a physiological stimulus for myocyte growth. Cell growth increased following the onset of contraction when measured over 3 days. The rate of protein synthesis was accelerated in parallel by contraction, but the rate of protein degradation remained similar to rates in noncontracting cells. The capacity for protein synthesis was estimated by total RNA content and was increased in contracting as compared with KCl-arrested cells. This increase was accompanied by faster rates of RNA synthesis as determined from the incorporation of [3H]uridine into RNA and the specific activity of the cellular UTP pool. The rate of RNA degradation was accelerated during contraction but the difference between the rates of RNA synthesis and degradation resulted in net RNA accumulation of 49% after 3 days. These data demonstrated that 1) contractile activity stimulated myocyte growth through an increased capacity for protein synthesis and 2) the increased capacity for protein synthesis involved acceleration of the rate of RNA synthesis. Since enhancement of protein synthetic capacity is a common feature of myocyte hypertrophy in vivo and in vitro, this model can be used to examine the regulation of ribosome synthesis during hypertrophic growth.

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Role of contraction in the structure and growth of neonatal rat cardiocytes

Cited by 21 publications

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Specialization at the Z line of cardiac myocytes

Specialization at the Z line of cardiac myocytes

Genetic, neurohumoral, and hemodynamic influences on spontaneously hypertensive rat heart development in oculo.

Contraction modulates the capacity for protein synthesis during growth of neonatal heart cells in culture.

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