δ-OPIOID RECEPTOR STIMULATION ENHANCES THE GROWTH OF NEONATAL RAT VENTRICULAR MYOCYTES VIA THE EXTRACELLULAR SIGNAL-REGULATED KINASE PATHWAY

Androgens appear to enhance, whereas estrogens mitigate, cardiac hypertrophy. However, signaling pathways in cells for short (3 min) and longer term (48 h) treatment with 17β-estradiol (E2) or 5α-dihydrotestosterone (DHT) are understudied. We compared the effect of adrenergic stimulation by norepinephrine (NE; 1 μM) alone or in combination with DHT (10 nM) or E2 (10 nM) treatment in neonatal rat ventricular myocytes (NRVMs) by cell area, protein synthesis, sarcomeric structure, gene expression, phosphorylation of extracellular signal-regulated (ERK), and focal adhesion kinases (FAK), and phospho-FAK nuclear localization. NE alone elicited the expected hypertrophy and strong sarcomeric organization, and DHT alone gave a similar but more modest response, whereas E2 did not alter cell size. Effects of NE dominated when used with either E2 or DHT with all combinations. Both sex hormones alone rapidly activated FAK but not ERK. Long-term or brief exposure to E2 attenuated NE-induced FAK phosphorylation, whereas DHT had no effect. Neither hormone altered NE-elicited ERK activation. Longer term exposure to E2 alone reduced FAK phosphorylation and reduced nuclear phospho-FAK, whereas its elevation was seen in the presence of NE with both sex hormones. The mitigating effects of E2 on the NE-elicited increase in cell size and the hypertrophic effect of DHT in NRVMs are in accordance with results observed in whole animal models. This is the first report of rapid, nongenomic sex hormone signaling via FAK activation and altered FAK trafficking to the nucleus in heart cells.

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CARP Plays a Key Role in Cellular Growth Under Hypertrophic Stimuli in Neonatal Rat Ventricular Myocytes

Vanderbilt Undergraduate Research Journal ◽

10.15695/vurj.v9i0.3790 ◽

2013 ◽

Vol 9 ◽

Author(s):

Tara A Shrout

Keyword(s):

Gene Expression ◽

Ventricular Myocytes ◽

Cellular Growth ◽

Neonatal Rat ◽

Transcriptional Level ◽

Dual Nature ◽

Hypertrophic Growth ◽

Rat Ventricular Myocytes ◽

Neonatal Rat Ventricular Myocytes ◽

Over Time

Cardiac hypertrophy is a growth process that occurs in response to stress stimuli or injury, and leads to the induction of several pathways to alter gene expression. Under hypertrophic stimuli, sarcomeric structure is disrupted, both as a consequence of gene expression and local changes in sarcomeric proteins. Cardiac-restricted ankyrin repeat protein (CARP) is one such protein that function both in cardiac sarcomeres and at the transcriptional level. We postulate that due to this dual nature, CARP plays a key role in maintaining the cardiac sarcomere. GATA4 is another protein detected in cardiomyocytes as important in hypertrophy, as it is activated by hypertrophic stimuli, and directly binds to DNA to alter gene expression. Results of GATA4 activation over time were inconclusive; however, the role of CARP in mediating hypertrophic growth in cardiomyocytes was clearly demonstrated. In this study, Neonatal Rat Ventricular Myocytes were used as a model to detect changes over time in CARP and GATA4 under hypertrophic stimulation by phenylephrine and high serum media. Results were detected by analysis of immunoblotting. The specific role that CARP plays in mediating cellular growth under hypertrophic stimuli was studied through immunofluorescence, which demonstrated that cardiomyocyte growth with hypertrophic stimulation was significantly blunted when NRVMs were co-treated with CARP siRNA. These data suggest that CARP plays an important role in the hypertrophic response in cardiomyocytes.

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Regulation of Ras·GTP Loading and Ras-Raf Association in Neonatal Rat Ventricular Myocytes by G Protein-coupled Receptor Agonists and Phorbol Ester

Journal of Biological Chemistry ◽

10.1074/jbc.274.28.19762 ◽

1999 ◽

Vol 274 (28) ◽

pp. 19762-19770 ◽

Cited By ~ 74

Author(s):

Antonio Chiloeches ◽

Hugh F. Paterson ◽

Richard Marais ◽

Angela Clerk ◽

Christopher J. Marshall ◽

...

Keyword(s):

G Protein ◽

Phorbol Ester ◽

Ventricular Myocytes ◽

Neonatal Rat ◽

G Protein Coupled Receptor ◽

Rat Ventricular Myocytes ◽

Receptor Agonists ◽

Neonatal Rat Ventricular Myocytes ◽

G Protein Coupled

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Abstract 15280: Comparisons of Action Potentials and Ionic Currents Between Neonatal Rat Ventricular Myocytes and Adult Zebrafish Ventricular Myocytes

Circulation ◽

10.1161/circ.130.suppl_2.15280 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Adonis Z Wu ◽

Shien-Fong Lin ◽

Sheng-Nan Wu

Keyword(s):

Electrical Properties ◽

Ventricular Myocytes ◽

Ionic Currents ◽

Firing Frequency ◽

Neonatal Rat ◽

Adult Zebrafish ◽

Patch Clamp Technique ◽

Action Current ◽

Rat Ventricular Myocytes ◽

Neonatal Rat Ventricular Myocytes

Introduction: Zebrafish heart is established as a model to investigate cardiac electrical abnormalities. However, electrical properties of adult zebrafish cardiomyocytes are not sufficiently characterized. Hypothesis: In this study, by comparing the electrical properties between neonatal rat ventricular myocytes (NRVMs) and adult zebrafish ventricular myocytes (AZVMs), we intended to characterize the action potential (AP), action current (AC) and the properties of Na + current ( I Na ) in AZVMs. Methods: We used patch-clamp technique to characterize the electrical properties, including AP, AC and I Na , in cultured NRVMs and freshly isolated AZVMs. Results: NVRMs showed larger AP amplitude (119±6 vs. 79±4mV, p<.05) but shorter AP duration (APD 90 , 136±11 vs. 213±19 ms, p<.05) than those of AZVMs. The AP duration exhibited marked frequency-dependent alterations in AZVMs. Under the slow pacing rate, early after-depolarizations (EAD) emerged under slow pacing rate with 0.05 Hz. In cell-attached voltage-clamp recordings made from AZVMs, ACs could be elicited by +10 mV steps. As the depolarization step increased to +70 mV, the latency for appearance of ACs was progressively reduced from >123 ms to 9.8 ms. The presence of spontaneous ACs was monitored in spontaneously beating NRVMs and AZVMs. The AC amplitude in NRVMs was larger compared to that in AZVMs (17.3±2.1 vs. 11.6±1.1 pA, p<.05), although firing frequency of AC in NRVMs is higher than in AZVMs (1.13±0.09 vs. 0.38±0.03 Hz, p<.05). The lowering effect of ranolazine, a I Na antagonist, on firing frequency was significantly larger in NRVMs (1.13±0.09 to 0.31±0.02 Hz, p<.05) than in AZVMs (0.38±0.03 to 0.27±0.02 Hz). There was a hyperpolarizing shift of peak I Na in AZVM compared to NRVM. Conclusions: Our results demonstrated major differences in the cellular electrical behavior between AZVMs and NRVMs.

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