TY - JOUR
T1 - Selectivity and gating of the type L potassium channel in mouse lymphocytes
AU - Shapiro, Mark S.
AU - DeCoursey, Thomas E.
PY - 1991/6
Y1 - 1991/6
N2 - Type l voltage-gated K+ channels in murine lymphocytes were studied under voltage clamp in cell-attached patches and in the whole-cell configuration. The kinetics of activation of whole-cell currents during depolarizing pulses could be fit by a single exponential after an initial delay. Deactivation upon repolarization of both macroscopic and microscopic currents was mono-exponential, except in Rb-Ringer or Cs-Ringer solution in which tail currents often displayed "hooks," wherein the current first increased or remained constant before decaying. In some cells type l currents were contaminated by a small component due to type n K+ channels, which deactivate ∼10 times slower than type l channels. Both macroscopic and single channel currents could be dissected either kinetically or pharmacologically into these two K+ channel types. The ionic selectivity and conductance of type l channels were studied by varying the internal and external permeant ion. With 160 mM K+ in the cell, the relative permeability calculated from the reversal potential with the Goldman-Hodgkin-Katz equation was K+ (≡1.0) > Rb+ (0.76) > NH4+ = Cs+ (0.12) ≫ Na+ (< 0.004). Measured 30 mV negative to the reversal potential, the relative conductance sequence was quite different: NH4+ (1.5) > K+ (≡ 1.0) > Rb+ (0.5) > Cs+ (0.06) ≫ Na+, Li+, TMA+ (unmeasurable). Single channel current rectification resembled that of the whole-cell instantaneous I-V relation. Anomalous mole-fraction dependence of the relative permeability PNH4/PK was observed in NH4+-K+ mixtures, indicating that the type l K+ channel is a multi-ion pore. Compared with other K+ channels, lymphocyte type l K+ channels are most similar to "gf2" channels in myelinated nerve.
AB - Type l voltage-gated K+ channels in murine lymphocytes were studied under voltage clamp in cell-attached patches and in the whole-cell configuration. The kinetics of activation of whole-cell currents during depolarizing pulses could be fit by a single exponential after an initial delay. Deactivation upon repolarization of both macroscopic and microscopic currents was mono-exponential, except in Rb-Ringer or Cs-Ringer solution in which tail currents often displayed "hooks," wherein the current first increased or remained constant before decaying. In some cells type l currents were contaminated by a small component due to type n K+ channels, which deactivate ∼10 times slower than type l channels. Both macroscopic and single channel currents could be dissected either kinetically or pharmacologically into these two K+ channel types. The ionic selectivity and conductance of type l channels were studied by varying the internal and external permeant ion. With 160 mM K+ in the cell, the relative permeability calculated from the reversal potential with the Goldman-Hodgkin-Katz equation was K+ (≡1.0) > Rb+ (0.76) > NH4+ = Cs+ (0.12) ≫ Na+ (< 0.004). Measured 30 mV negative to the reversal potential, the relative conductance sequence was quite different: NH4+ (1.5) > K+ (≡ 1.0) > Rb+ (0.5) > Cs+ (0.06) ≫ Na+, Li+, TMA+ (unmeasurable). Single channel current rectification resembled that of the whole-cell instantaneous I-V relation. Anomalous mole-fraction dependence of the relative permeability PNH4/PK was observed in NH4+-K+ mixtures, indicating that the type l K+ channel is a multi-ion pore. Compared with other K+ channels, lymphocyte type l K+ channels are most similar to "gf2" channels in myelinated nerve.
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M3 - Article
C2 - 1875188
AN - SCOPUS:0026328378
SN - 0022-1295
VL - 97
SP - 1227
EP - 1250
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 6
ER -