Growth effects of electrically stimulated contraction on adult feline cardiocytes in primary culture

Abstract

The purpose of this study was to determine effects of long-term electrical stimulation of cardiocyte contraction on protein synthesis rates and total protein content. Adult feline cardiocytes were plated on laminin-coated culture trays and maintained in a serum-free medium consisting of M199 supplemented with ascorbate, bovine serum albumin, creatine, carnitine, taurine, and 10(-7) M recombinant insulin. Cardiocytes were electrically stimulated to contract with use of continuous electrical pulses of alternating polarity at a frequency of 1 Hz and pulse duration of 5 ms. Nonstimulated cardiocytes are normally quiescent and were used as the control group. In control quiescent cardiocytes, protein synthesis rate decreased by 14% between days 1 and 4 in culture and then remained stable through day 7. In electrically stimulated cardiocytes, protein synthesis rates increased by 19% between days 1 and 7. Protein synthesis rates were 18% higher on day 4 and 43% higher on day 7 in electrically stimulated than in quiescent cardiocytes. Protein content per cell was determined by measuring total fluorescence per cell by use of confocal microscopy of fluorescein isothiocyanate-stained cells. Electrical stimulation significantly increased cellular protein content by 52% after 7 days compared with controls. Quiescent and electrically stimulated cardiocytes remained rod shaped, retained their myofibrillar architecture, and were responsive to electrical stimulation over the 7-day period. These data demonstrated that electrically stimulated contraction of adult cardiocytes resulted in cell growth, as assessed by an increase in protein content per cell over 7 days in culture. This increase was due, at least in part, to an acceleration of steady-state protein synthesis rates.

Role of transiently altered sarcolemmal membrane permeability and basic fibroblast growth factor release in the hypertrophic response of adult rat ventricular myocytes to increased mechanical activity in vitro.

“…1). Similar changes in cell morphology have recently been reported in adult feline ventricular myocytes continually paced at 1 Hz for 7 d in defined serum-free medium (37). These changes were unexpected (by us) and resembled the early stages of phenotypic adaptation of quiescent adult ventricular myocytes cultured in serum-containing medium (i.e., at 24-48 h after isolation) (35,38,39).…”

“…However, the experimental protocol described here was initiated at least 6 h after myocyte isolation to permit some recovery from the dissociation procedure to occur. In our experience (31) and in the data reported by Kato et al (37), neither myocyte viability nor the number of rodshaped cells differed between paced and quiescent cells after 4-7 d of culture. Also, we have tracked the uptake of rat albumin into the beating adult rat heart in situ (60).…”

“…Kubisch et al (52) have also reported that increased immediate early gene transcription in adult ventricular myocytes induced by continual pacing could also be prevented by BDM. Importantly, Kato et al (37) also report that, whereas a small decline ‫ف(‬ 15%) in protein synthesis rates and total cellular protein content could be detected in quiescent myocytes during the first week of primary culture, both protein synthesis rates and total cellular protein content were significantly higher (by 40-50%) in paced compared with control myocytes. These data indicate that, whereas a limited degree of atrophy does occur over 1 wk in quiescent cells, there is a significant amount of hypertrophic growth in paced cells.…”

Functional assembly of engineered myocardium by electrical stimulation of cardiac myocytes cultured on scaffolds

“…4, Phase 2) induced hyperpolarization at the anode end of the cell and depolarization at the cathode end of the cell (16), such that the cells aligned with the electrical field lines were subjected to the largest voltage difference and were likely the first ones to generate action potentials and contract. Processes forming at the cells' ends (19) promoted the establishment of gap junctions, propagation of pacing signals, and generation of action potentials (Fig. 1E) that induced synchronous macroscopic contractions (Fig.…”

Interactive effects of surface topography and pulsatile electrical field stimulation on orientation and elongation of fibroblasts and cardiomyocytes

“…Chronic supra-threshold electrical field stimulation of cardiomyocytes in 2D was shown to preserve contractility [2], maintain calcium transients [3], promote hypertrophy [4], increase protein synthesis [5,6] and maintain action potential duration and maximum capture rate [7]. The beneficial effects of field stimulation were depended on the occurrence of contraction following field stimulated excitation, as evidenced by the lack of observed effects in the presence of excitation-contraction decouplers: verapamil or 2,3-butanedione monoxime [8].…”