Diversity of early afterdepolarizations in guinea pig myocytes: spatial characteristics of intracellular Ca2+ concentration.
We classified early afterdepolarizations (EADs) into subgroups according to the spatial features of the intracellular Ca2+ concentration ([Ca2+]i). Myocytes were enzymatically isolated from guinea pig ventricles. When fura-2 salt was applied through a whole cell patch pipette after the formation of a gigaohm seal, the membrane potential was measured using the current, clamp technique. When myocytes were loaded with fura-2 AM, the membrane potential was recorded with a conventional microelectrode technique. Spatio-temporal changes in fura-2 fluorescence and cell length were recorded simultaneously, using a digital TV system. EADs were induced after superfusion with potassium-free Tyrode solution. Irrespective of the fura-2 loading procedure, EADs could be classified into those with spatially synchronous fluorescence changes (n = 26 from eight hearts) and those with heterogeneous changes (n = 20 from three hearts). EADs with synchronous features took off from a higher membrane potential (> or = -34 mV) than EADs with heterogeneous features (< or = -57 mV). These results suggest that EADs have at least two constituents.
Miura
M
M
The First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Ishide
N
N
Numaguchi
H
H
Takishima
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004594:Electrophysiology; D006168:Guinea Pigs; D015640:Ion Channel Gating; D017136:Ion Transport; D008564:Membrane Potentials; D009206:Myocardium / Q000166:cytology; D016276:Ventricular Function
D002118:Calcium