Evidence for Ca-mediated inactivation of ICa in dialysed guinea-pig atrial cardioballs.
Ca current (ICa) was studied in cultured myocytes from right atria of adult guinea-pigs (cardioballs) by means of single low-resistance patch pipettes. K currents were blocked by dialysis of the cells with solutions containing Cs+ as main cation and extracellular TEA (70 mM). Under this condition membrane currents elicited by voltage clamp pulses of 200 ms in duration from -45 mV (holding potential) are net inward for depolarizations up to +55 mV without detectable contamination by outward current components. The peak inward current (ICa) has a maximum between +5 and +10 mV and reverses around +60 mV. Measurements of ICa tail currents obtained after clamp pulses of increasing duration to more and more positive membrane potentials suggest that ICa inactivation is not genuinely voltage-dependent.
Bechem
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M
Pott
L
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D000818:Animals; D001826:Body Fluids / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003956:Dialysis; D004562:Electrocardiography; D006168:Guinea Pigs; D006325:Heart Atria / Q000166:cytology; D007424:Intracellular Fluid / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D009206:Myocardium / Q000166:cytology*; D012508:Sarcolemma / Q000502:physiology
D007473:Ion Channels; D002118:Calcium