
TY  - JOUR
A1  - Kourie, J 
T1  - Voltage-Dependence of Extracellular Ca<sup>2+</sup>-Induced Modification in Properties of the Inward Rectifying K<sup>+</sup> Channels in the Plasma Membrane of Mesophyll Protoplasts of <I>Avena sativa</I>
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1996
VL  - 23
IS  - 3
SP  - 349
EP  - 359
KW  - Extracellular Ca2+, inward rectification, Avena sativa
UR  - https://doi.org/10.1071/PP9960349 
N2  - Data obtained using the whole-celi configuration of the patch-clamp technique reveal that characteristics of the inward rectifying K+ current across the plasma membrane of protoplasts isolated from mesophyll cells of leaves of oat (Avena sativa) are modified by increasing concentrations or removing the extracellular Ca2+.     The whole-cell membrane current reveals two components. The first component an initial current II* which is the sum of two currents: (a) a linear ohmic leak current passing through non-gated channels, liNGC, and (b) a rectifying inward K+ current passing through inward rectifying gated K+ channels, IKi, that are instantaneously open. The second component of the membrane current at the steady state Iss is a time-dependent K+ current IKss defined as Iss-IiNGC and passes through inward rectifying gated K+ channels. The tail K+ current, IKT, is also defined as IT-IiNGC.     Raising external calcium concentration, [Ca2+]o, from 0.1 mM to 10 mM blocked the inward rectifying currents IKi, IKss and IKT. The voltage-dependence of the activation time constant (&#964;a) for time-dependent KC current IKss was not altered significantly by increasing [Ca2+]o whereas the deactivation time constant (&#964;d) of the IKT increased from 16 ms to 30 ms at a Vm of -100 mV.     Removal of [Ca2+]o increased the amplitude and altered the characteristics of the inward rectifying K+ current. Ten minutes after the removal of [Ca2+]o the increase in IKi was 3.5-fold larger than the increase in IKss. Furthermore, removing [Ca2+]o hastened the activation of IKss and the deactivation of IKT. However, the deactivation time constant (Td) remained dependent on membrane voltage (Vm).    Extracellular Ca2+ may modulate the function of mesophyll cells by regulating K+ transport through the inward rectifying K+ channels and this may have significant implications for photosynthesis and cell expansion. 
ER  -

