Open AccessReopening of L‐type calcium channels in human ventricular myocytes during applied epicardial action potentials
Author(s) -
Fülöp L.,
Bányász T.,
Magyar J.,
Szentandrássy N.,
Varró A.,
Nánási P. P.
Publication year - 2004
Publication title -
acta physiologica scandinavica
Language(s) - English
Resource type - Journals
eISSN - 1365-201X
pISSN - 0001-6772
DOI - 10.1046/j.0001-6772.2003.01223.x
Subject(s) - repolarization , electrophysiology , myocyte , chemistry , patch clamp , biophysics , medicine , biology
Aims: Present study was performed to compare the dynamics of human L‐type calcium current ( I Ca,L ) flowing during rectangular voltage pulses, voltage ramps, and action potentials (APs) recorded from epicardiac and endocardiac canine ventricular cells. Methods: ICa,L was recorded in single myocytes isolated from undiseased human hearts using the whole cell voltage clamp technique. Results: The decay of I Ca,L was monotonic when using rectangular pulses or endocardial APs as voltage commands, whereas the current became double‐peaked (displaying a second rise and fall) during epicardial (EPI) APs or voltage ramps used to mimic EPI APs. These I Ca,L profiles were associated with single‐hooked and double‐hooked phase‐plane trajectories, respectively. No sustained current was observed during the AP commands. Kinetics of deactivation and recovery from inactivation of human I Ca,L were determined using twin‐pulse voltage protocols and voltage ramps, and the results were similar to those obtained previously in canine cells under identical experimental conditions. Conclusions: ICa,L can inactivate partially before and deactivate during the phase‐1 repolarization of the epicardiac AP, and reopening of these channels seems to be associated with formation of the dome.