Hypertrophy of isolated adult feline heart cells following beta-adrenergic-induced beating

Abstract

Catecholamine-induced beating and myocardial hypertrophy were evaluated in isolated adult feline cardiomyocytes maintained in culture for up to 30 days. Adult feline cardiomyocytes were used in this study because they displayed several unique characteristics that facilitated assessment of factors regulating cardiomyocyte hypertrophy in vitro. These characteristics included the following. 1) A single heart provides a high yield of 20-40 x 10(6) calcium-tolerant rod-shaped myocytes. 2) In culture, isolated adult feline cardiomyocytes maintain a stable population of differentiated myocytes that could be maintained without the dramatic loss of cell number, DNA content, or cell structure seen in adult rat cardiomyocyte cultures. 3) Cultured feline cardiomyocytes remained quiescent in culture unless appropriately stimulated to begin beating. 4) Sustained regular beating activity could be readily initiated up to 3 wk in culture by addition of 1 x 10(-5) M isoproterenol, other beta-adrenergic agonists, or agents known to elevate adenosine 3',5'-cyclic monophosphate. Beating could be maintained indefinitely in the presence of isoproterenol, but ceased upon removal of isoproterenol from the medium. Initiation of beating in 7-day-old cultures resulted in a profound restructuring of cardiomyocyte morphology compared with quiescent cultures. Beating heart cells were 66% larger with increased protein content, and they had significantly greater development of striated myofibrillar structure than quiescent myocytes at the same age in culture. We conclude that maintenance of an organized myofibrillar structure in cultured adult cardiac myocytes requires activation of intrinsic beating. Cardiomyocyte hypertrophy also develops following beta-adrenergic activation of beating, but it is unclear whether beating per se is required for inducing hypertrophy in isolated adult cardiomyocytes in vitro.

Methamphetamine induces an increase in cell size and reorganization of myofibrils in cultured adult rat cardiomyocytes

“…It has been reported that cardiac hypertrophy characterized by an increase in cell size was induced by catecholamines (Simpson et al 1982;Simpson and McGrath 1983;Simpson 1985;Tang et al 1987;Clark et al 1991). Therefore, to confirm whether cellular hypertrophy occurred in ARCs used in this experiment, ARCs were exposed to 0.1, 1.0 or 2.0 µM l-norepinephrine bitartrate (NE, Wako, Japan) for 7 days (from days 6 to 13 in culture).…”

Regulation of Cardiac Myocyte Protein Turnover and Myofibrillar Structure In Vitro by Specific Directions of Stretch

“…27 Data were normalized to the relative amount of protein-bound radioactivity observed in unstretched cultures of spontaneously beating myocytes and were pooled from 4 experiments. Two-way ANOVA was used to examine the effects of NIFED or ISO treatment in the presence of specific directions of stretch.…”

Morphological and functional characteristics of models of experimental myocardial injury induced by isoproterenol

“…Cardiac remodeling resulting from increased heart rate and hemodynamic overload, or increased workload and increased wall tension (Lijnen et al 2000;Ozaki et al 2002) initiates cardiac hypertrophy as evidenced by both in vivo (Benjamin et al 1989;Zierhut and Zimmer 1989;Boluyt et al 1995) and in vitro (Clark et al 1991;Zou et al 1999) studies. Chronic stimulation of β-adrenergic receptor associated with cardiac overload and congestive heart failure (Bristow 2000) may cause progressive myocyte dysfunction, cell loss or cardiac chamber remodeling (Limbird and Voughan 1999) as it has been demonstrated in humans and experimental animals.…”