scholarly journals Thyroid hormone regulation of transmembrane signalling in neonatal rat ventricular myocytes by selective alteration of the expression and coupling of G-protein α-subunits

1995 ◽  
Vol 307 (3) ◽  
pp. 831-841 ◽  
Author(s):  
S W Bahouth
Keyword(s):  
Thyroid Hormone ◽  
Adenylate Cyclase ◽  
G Protein ◽  
G Proteins ◽  
Half Life ◽  
Ventricular Myocytes ◽  
Neonatal Rat ◽  
Rat Ventricular Myocytes ◽  
Gs Alpha ◽  
Neonatal Rat Ventricular Myocytes

Thyroid hormone exerts profound effects on the activity of the hormone-sensitive adenylate cyclase system in the heart. Distinct guanine nucleotide-binding regulatory proteins (G-proteins) mediate stimulatory and inhibitory influences on adenylate cyclase activity. To examine whether the effects of thyroid hormone on adenylate cyclase involve specific changes in G-protein subunit expression, the influence of tri-iodothyronine (T3) on the biosynthesis and activity of G-proteins in neonatal rat ventricular myocytes was determined. In myocytes challenged with T3 for 5 days, Gs alpha levels increased by 4 +/- 0.5-fold, whereas Gi2 alpha levels declined by more than 80%. T3 down-regulated Gi2 alpha mRNA by 60% within 3 days, but had no effect on Gs alpha mRNA. The basis for the decline in Gi2 alpha mRNA was the T3-mediated suppression of Gi2 alpha gene transcription by 80 +/- 9% within 4 h. The decline in Gi2 alpha mRNA in response to T3 produced a 2-fold decrease in relative rate of synthesis of Gi2 alpha but not in its half-life (46 +/- 7 h). Gs alpha synthesis was not altered by T3, but the half-life of Gs alpha increased from 50 +/- 6 h in control cells to 72 +/- 8 h in T3-treated cells. In addition, T3 provoked the translocation of Gs alpha from the cytoplasmic to the membranous compartment. Membranous Gs alpha increased from 30 +/- 6% to 61 +/- 7% of total cellular Gs alpha, whereas cytoplasmic Gs alpha declined from 68 +/- 6% to 33 +/- 8% within 1 day of exposure to T3. T3-mediated up-regulation of Gs alpha enhanced the activation of myocardial adenylate cyclase by the stimulatory pathway whereas the down-regulation of Gi2 alpha attenuated the deactivation of myocardial adenylate cyclase by the inhibitory pathway.

Coupling of ATP-sensitive K+ channels to A1 receptors by G proteins in rat ventricular myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. H820-H826 ◽  
Author(s):  
G. E. Kirsch ◽  
J. Codina ◽  
L. Birnbaumer ◽  
A. M. Brown
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Ventricular Myocytes ◽  
Neonatal Rat ◽  
Extracellular Adenosine ◽  
Rat Ventricular Myocytes ◽  
Receptor Coupling ◽  
Neonatal Rat Ventricular Myocytes ◽  
Gamma S ◽  
Ischemic Muscle

ATP-sensitive K+ (K+[ATP]) current is thought to be regulated by GTP-binding proteins (G proteins), but the pathways that couple receptor, G protein, and channel have not been defined. We studied regulation of tolbutamide-sensitive K+[ATP] current in neonatal rat ventricular myocytes. Application of 0.1 mM ATP to the intracellular side of membrane patches reduced K+ [ATP] channel activity, and addition of the nonhydrolyzable GTP analogue guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) at 0.1 mM restored activity. Application of 0.1 mM intracellular GTP plus 10 microM extracellular adenosine or 100 nM N6-cyclohexyladenosine had the same effect as GTP gamma S; hence K+[ATP] channels may be coupled to adenosine receptors via G proteins. To determine which G protein, we applied G alpha subunits, preactivated with GTP gamma S to the cytoplasmic side of membrane patches, and found that alpha i1, alpha i2, and alpha i3 mimicked the effect of GTP gamma S, but not alpha o or Gs, suggesting that Gi alpha acts via a membrane-delimited pathway. Adenosine receptor coupling may be important for activating K+[ATP] channels in ischemic muscle.

Thyroid hormone stimulates 5′-ecto-nucleotidase of neonatal rat ventricular myocytes

2004 ◽  
Vol 265 (1/2) ◽  
pp. 195-201 ◽  
Author(s):  
Marcela Sorelli Carneiro-Ramos ◽  
Vanessa Beatriz da Silva ◽  
Marconi Barbosa Coutinho Júnior ◽  
Ana Maria Oliveira Battastini ◽  
João José Freitas Sarkis ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Ventricular Myocytes ◽  
Neonatal Rat ◽  
Rat Ventricular Myocytes ◽  
Neonatal Rat Ventricular Myocytes

Beta-receptor-adenylate cyclase coupling in hypoxic neonatal rat ventricular myocytes

1989 ◽  
Vol 256 (4) ◽  
pp. H1209-H1217 ◽  
Author(s):  
F. T. Thandroyen ◽  
K. Muntz ◽  
T. Rosenbaum ◽  
B. Ziman ◽  
J. T. Willerson ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
Ventricular Myocytes ◽  
Neonatal Rat ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Binding Properties ◽  
Rat Ventricular Myocytes ◽  
Beta Receptor ◽  
Neonatal Rat Ventricular Myocytes

This study investigated the influence of hypoxia on alterations in the beta-adrenergic receptor-adenylate cyclase system. Cultured neonatal rat ventricular myocytes were subjected to normoxia (incubator PO2 135-145 mmHg) or hypoxia (incubator PO2 0-14 mmHg) and, in crude membrane preparations, beta-receptor binding properties were measured with [125I]iodocyanopindolol and adenylate cyclase activity by radioimmunoassay. Hypoxia of 30 min in duration caused no alteration in beta-receptor density (Bmax 75 +/- 11 vs. 71 +/- 12 fmol/mg protein) but increased adenylate cyclase activity under basal conditions and during stimulation with l-isoproterenol, 5'-guanylimidotriphosphate [Gpp(NH)p] 5 X 10(-5) M, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + guanosine 5'-triphosphate (GTP) 5 X 10(-5) M gave 221 +/- 34 vs. 143 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. After 60 min of hypoxia, adenylate cyclase activity was no longer increased. Hypoxia of 120-150 min duration increased Bmax by 64% (73 +/- 8 to 120 +/- 11 fmol/mg protein, P less than 0.05 vs. normoxia) but decreased adenylate cyclase activity during stimulation with isoproterenol, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + GTP 5 X 10(-5) M gave 107 +/- 12 vs. 148 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. Reoxygenation for 15 min following 120-150 min of hypoxia reversed the increased beta-receptor numbers and decreased adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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.

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

Circulation ◽  
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.

scholarly journals Chronotropic Response of Cultured Neonatal Rat Ventricular Myocytes to Short-Term Fluid Shear

2006 ◽  
Vol 46 (2) ◽  
pp. 113-122 ◽  
Author(s):  
Ilka Lorenzen-Schmidt ◽  
Geert W. Schmid-Schönbein ◽  
Wayne R. Giles ◽  
Andrew D. McCulloch ◽  
Shu Chien ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Neonatal Rat ◽  
Fluid Shear ◽  
Short Term ◽  
Chronotropic Response ◽  
Rat Ventricular Myocytes ◽  
Neonatal Rat Ventricular Myocytes

scholarly journals Hexokinase–mitochondrial interactions regulate glucose metabolism differentially in adult and neonatal cardiac myocytes

2013 ◽  
Vol 142 (4) ◽  
pp. 425-436 ◽  
Author(s):  
Guillaume Calmettes ◽  
Scott A. John ◽  
James N. Weiss ◽  
Bernard Ribalet
Keyword(s):  
Cardiac Tissue ◽  
Ventricular Myocytes ◽  
Glycogen Synthesis ◽  
Neonatal Rat ◽  
Metabolic Profiles ◽  
Rat Ventricular Myocytes ◽  
Glycolytic Activity ◽  
Extracellular Glucose ◽  
Functional Consequences ◽  
Neonatal Rat Ventricular Myocytes

In mammalian tumor cell lines, localization of hexokinase (HK) isoforms to the cytoplasm or mitochondria has been shown to control their anabolic (glycogen synthesis) and catabolic (glycolysis) activities. In this study, we examined whether HK isoform differences could explain the markedly different metabolic profiles between normal adult and neonatal cardiac tissue. We used a set of novel genetically encoded optical imaging tools to track, in real-time in isolated adult (ARVM) and neonatal (NRVM) rat ventricular myocytes, the subcellular distributions of HKI and HKII, and the functional consequences on glucose utilization. We show that HKII, the predominant isoform in ARVM, dynamically translocates from mitochondria and cytoplasm in response to removal of extracellular glucose or addition of iodoacetate (IAA). In contrast, HKI, the predominant isoform in NRVM, is only bound to mitochondria and is not displaced by the above interventions. In ARVM, overexpression of HKI, but not HKII, increased glycolytic activity. In neonatal rat ventricular myocytes (NVRM), knockdown of HKI, but not HKII, decreased glycolytic activity. In conclusion, differential interactions of HKI and HKII with mitochondria underlie the different metabolic profiles of ARVM and NRVM, accounting for the markedly increased glycolytic activity of NRVM.

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