Low-voltage-activated calcium channels in human retinoblastoma cells.
Retinoblastoma cells represent pluripotent neural-progenitor cells which, if induced to differentiate, express many features of mature human retinal neurons. Ca channel currents were recorded from isolated, undifferentiated human retinoblastoma Y79 cells in a bath solution containing 20 mM BaCl2 using whole-cell patch-clamp pipettes containing CsCl. The transient, macroscopic currents inactivated with a time constant of about 20 ms at -20 mV and had other properties similar to low-voltage-activated calcium channels described in other cell types: Activation curves fit by the Boltzmann relation had a midpoint of -32 mV and a slope factor of 6.8 mV (-80 mV holding potential) and inactivation curves had a midpoint of -40 mV and a slope factor of 3.7 mV. Non-stationary fluctuation analysis of the currents performed over a 2 kHz bandwidth indicated that each channel contributed 0.44 pA to the macroscopic transient current at -20 mV, suggesting a unitary conductance of about 7 pS.
Barnes
S
S
Neuroscience Research Group, University of Calgary, Faculty of Medicine, Alberta, Canada.
Haynes
L W
LW
D015220:Calcium Channels / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D004594:Electrophysiology; D006801:Humans; D009474:Neurons / Q000502:physiology*; D012160:Retina / Q000166:cytology*; D012175:Retinoblastoma; D014407:Tumor Cells, Cultured
D015220:Calcium Channels