Action potentials, ion channel currents and transverse tubule density in adult rabbit ventricular myocytes maintained for 6 days in cell culture.
Adult rabbit ventricular myocytes were cultured in a basic medium (Medium 199) for up to 6 days to assess preservation of morphology and ion channel currents. In culture, cells remained rod shaped and striated but their ends became progressively rounded. Cell cross-sectional area declined slightly (by 14%) over the first 24 h, in contrast, whole-cell capacitance (which reflects external surface membrane plus membrane infoldings) decreased by 42% over the same time. Using whole-cell patch-clamp, we observed that the typical "N" shape steady-state current-voltage (I-V) relation became flattened after 24 h in culture. L-type Ca channel density was assessed as barium flux (IBa,L) via the channel. IBa,L (normalised to cell capacitance) declined by 50% after 24 h and recovered partially by days 4 and 6. The density of inward rectifier K current declined by 54% after 24 h and showed no recovery subsequently. In contrast, there was no significant decline in the density of transient outward K current after 24 h, but it declined subsequently by 65% after 6 days. We speculate that the time course of change in each ion channel density may reflect a change in pattern of ion channel expression, or differential membrane loss since the density of transverse tubules decreased by 57% after 6 days in culture. These results suggest that even by 24 h in culture, ion channel density in myocytes has changed substantially from the acutely isolated state.
Mitcheson
J S
JS
Department of Physiology, University of Bristol, School of Medical Sciences, University Walk, Bristol, BS8 1TD, UK.
Hancox
J C
JC
Levi
A J
AJ
D000200:Action Potentials; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D003470:Culture Media; D004553:Electric Conductivity; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D011817:Rabbits
D015220:Calcium Channels; D003470:Culture Media; D007473:Ion Channels; D015221:Potassium Channels