Single-channel recordings of two types of calcium channels in rat pancreatic beta-cells.
Using the cell-attached configuration of the patch clamp technique, we have identified two different types of Ca channels in rat pancreatic beta-cell membranes. The two channels differ in single channel conductance, voltage dependence, and inactivation properties. The single-channel conductance, measured with 100 mM Ba2+ in the pipette, was 21.8 pS for the large channel and 6.4 pS for the small channel. The large-conductance channel is similar to the fast deactivating or L-type Ca channel described in other preparations. It is voltage dependent, has a threshold for activation around -30 mV, and can be activated from a holding potential of -40 mV. On the other hand, the small-conductance Ca channel is similar to the SD or T type Ca channel; it has a lower activation threshold, around -50 mV, and it can be inactivated by holding the membrane potential at -40 mV.
Sala
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University of Maryland School of Medicine, Department of Biophysics, Baltimore 21201.
Matteson
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D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D007515:Islets of Langerhans / Q000502:physiology*; D008564:Membrane Potentials; D051381:Rats
D015220:Calcium Channels