Na+ channels in cardiac and neuronal cells derived from a mouse embryonal carcinoma cell line.
1. Cells from a pluripotent murine embryonal carcinoma cell line (P19) were differentiated in vitro into cells with neurone- and cardiac-like phenotypes. Cells treated with 0.5 microM retinoic acid developed into neurone-like cells possessing extensive neurites. Dimethyl sulphoxide treatment (0.5%) produced large, spontaneously contracting cell aggregates with many properties of cardiac cells. 2. The neurone- and cardiac-like cells contained voltage-sensitive Na+ channels with properties similar to those of native neuronal and cardiac cells. 3. We used whole-cell patch clamp techniques to measure inward currents from the neurone- and cardiac-like cells. Undifferentiated (untreated) cells had only small inward currents (peak of -0.15 nA in 150 mM external Na+). The peak inward current in the neurone-like and cardiac-like cells was -1.2 nA (in 154 mM external Na+) and -2.8 nA (in only 46 mM Na+), respectively. These large currents were absent when the external solution contained no Na+. 4. Tetrodotoxin (TTX) blocked the Na+ currents in the neurone- and cardiac-like cells in a dose-dependent manner. The Kd for TTX block of the Na+ current in the neurone-like cells was 6.7 nM. The Na+ current in the cardiac-like cells was much more resistant to TTX; the half-blocking concentration was two orders of magnitude higher, 710 nM. 5. The kinetic properties of the Na+ channel currents in the neurone- and cardiac-like cells were similar but developed over somewhat different voltage ranges. The voltage sensitivity of activation was similar in both cell types but the activation mid-point voltage was different: -12 mV in the neuronal cells and -34 mV for cardiac cells. Inactivation of the neuronal Na+ channels had a mid-point near -47 mV and was more sensitive to the membrane voltage than inactivation of the cardiac channels. The mid-point of inactivation for the cardiac Na+ channels was -80 mV.
Arreola
J
J
Department of Physiology, University of Rochester, NY 14642.
Spires
S
S
Begenisich
T
T
D000818:Animals; D018236:Carcinoma, Embryonal / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004594:Electrophysiology; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010641:Phenotype; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D014212:Tretinoin; D004121:Dimethyl Sulfoxide