Tetrodotoxin-insensitive sodium channels in a cardiac cell line from a transgenic mouse

1992 ◽  
Vol 262 (3) ◽  
pp. C724-C730 ◽  
Author(s):  
A. Sculptoreanu ◽  
M. Morton ◽  
C. L. Gartside ◽  
S. D. Hauschka ◽  
W. A. Catterall ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cell Line ◽  
Transgenic Mouse ◽  
Sodium Channels ◽  
Sodium Current ◽  
Cardiac Cell ◽  
Dependent Protein Kinase ◽  
Electrophysiological Properties ◽  
Maximal Activation ◽  
Dependent Protein

The electrophysiological properties of a cardiac cell line (MCM1) originating from a transgenic mouse were characterized. The dominant current in these cells is a sodium current that is insensitive to concentrations of tetrodotoxin (TTX) up to 100 microM. It activates and inactivates rapidly with half-maximal activation at -40 mV and half-maximal inactivation at -79 mV. This sodium current is reduced by agents that increase intracellular adenosine 3',5'-cyclic monophosphate (cAMP) and activate cAMP-dependent protein kinase including isoproterenol, 8-bromo-cAMP, and isobutylmethylxanthine. The phenylalkylamine desmethoxyverapamil blocks the TTX-insensitive sodium current in MCM1 cells in both tonic and use-dependent fashion. Membrane depolarization enhances this block. It is proposed that the TTX-insensitive sodium current in these cells may be similar in origin to the embryonic type of TTX-insensitive sodium current described in other cardiac and skeletal muscle preparations.

C2C12 skeletal muscle cells adopt cardiac-like sodium current properties in a cardiac cell environment

2007 ◽  
Vol 292 (1) ◽  
pp. H439-H450 ◽  
Author(s):  
Eva Zebedin ◽  
Markus Mille ◽  
Maria Speiser ◽  
Touran Zarrabi ◽  
Walter Sandtner ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sodium Channel ◽  
Sodium Current ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Cardiac Cell ◽  
Sodium Currents ◽  
Current Function ◽  
Electrophysiological Properties ◽  
Cardiac Sodium Channel

Intracardiac transplantation of undifferentiated skeletal muscle cells (myoblasts) has emerged as a promising therapy for myocardial infarct repair and is already undergoing clinical trials. The fact that cells originating from skeletal muscle have different electrophysiological properties than cardiomyocytes, however, may considerably limit the success of this therapy and, in addition, cause side effects. Indeed, a major problem observed after myoblast transplantation is the occurrence of ventricular arrhythmias. The most often transient nature of these arrhythmias may suggest that, once transplanted into cardiac tissue, skeletal muscle cells adopt more cardiac-like electrophysiological properties. To test whether a cardiac cell environment can indeed modify electrophysiological parameters of skeletal muscle cells, we treated mouse C2C12 myocytes with medium preconditioned by primary cardiocytes and compared their functional sodium current properties with those of control cells. We found this treatment to significantly alter the activation and inactivation properties of sodium currents from “skeletal muscle” to more “cardiac”-like ones. Sodium currents of cardiac-conditioned cells showed a reduced sensitivity to block by tetrodotoxin. These findings and reverse transcription PCR experiments suggest that an upregulation of the expression of the cardiac sodium channel isoform Nav1.5 versus the skeletal muscle isoform Nav1.4 is responsible for the observed changes in sodium current function. We conclude that cardiomyocytes alter sodium channel isoform expression of skeletal muscle cells via a paracrine mechanism. Thereby, skeletal muscle cells with more cardiac-like sodium current properties are generated.

scholarly journals Expression of hormone-sensitive lipase and its regulation by adrenaline in skeletal muscle

1999 ◽  
Vol 340 (2) ◽  
pp. 459-465 ◽  
Author(s):  
Jozef LANGFORT ◽  
Thorkil PLOUG ◽  
Jacob IHLEMANN ◽  
Michele SALDO ◽  
Cecilia HOLM ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Soleus Muscle ◽  
Lipase Activity ◽  
Glycogen Phosphorylase ◽  
Hormone Sensitive Lipase ◽  
Dependent Protein Kinase ◽  
Dependent Protein ◽  
Hormone Sensitive ◽  
Neutral Lipase

The enzymic regulation of triacylglycerol breakdown in skeletal muscle is poorly understood. Western blotting of muscle fibres isolated by collagenase treatment or after freeze-drying demonstrated the presence of immunoreactive hormone-sensitive lipase (HSL), with the concentrations in soleus and diaphragm being more than four times the concentrations in extensor digitorum longus and epitrochlearis muscles. Neutral lipase activity determined under conditions optimal for HSL varied directly with immunoreactivity. Expressed relative to triacylglycerol content, neutral lipase activity in soleus muscle was about 10 times that in epididymal adipose tissue. In incubated soleus muscle, both neutral lipase activity against triacylglycerol (but not against a diacylglycerol analogue) and glycogen phosphorylase activity increased in response to adrenaline (epinephrine). The lipase activation was completely inhibited by anti-HSL antibody and by propranolol. The effect of adrenaline could be mimicked by incubation of crude supernatant from control muscle with the catalytic subunit of cAMP-dependent protein kinase, while no effect of the kinase subunit was seen with supernatant from adrenaline-treated muscle. The results indicate that HSL is present in skeletal muscle and is stimulated by adrenaline via β-adrenergic activation of cAMP-dependent protein kinase. The concentration of HSL is higher in oxidative than in glycolytic muscle, and the enzyme is activated in parallel with glycogen phosphorylase.

scholarly journals The phosphorylation of troponin I from cardiac muscle

1975 ◽  
Vol 149 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H A Cole ◽  
S V Perry
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cardiac Muscle ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Phosphorylase Kinase ◽  
Dependent Protein Kinase ◽  
Dependent Protein

1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.

Up-regulation of functional voltage-dependent sodium channels by cyclic AMP-dependent protein kinase in adrenal medulla

1996 ◽  
Vol 709 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Tomoaki Yuhi ◽  
Akihiko Wada ◽  
Ryuichi Yamamoto ◽  
Toshihiko Yanagita ◽  
Hiromi Niina ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Sodium Channels ◽  
Adrenal Medulla ◽  
Dependent Protein Kinase ◽  
Voltage Dependent ◽  
Dependent Protein
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