Teisseyre A, Mozrzymas J W
Department of Biophysics, Wrocław Medical University, Wrocław, Poland.
J Physiol Pharmacol. 2006 Mar;57(1):131-47.
In the present study we applied the whole-cell patch-clamp technique to study the influence of extracellular pH (pH(o)) on the modulatory effect exerted by zinc ions (Zn(2+)) on voltage-gated potassium channels Kv1.3 expressed in human lymphocytes. Obtained data provide evidence that lowering of pH(o) from the 7.35 to 6.4 slowed significantly the current activation rate, shifted the activation midpoint by about 16 mV towards positive membrane potentials and reduced the current amplitude to about 0.55 of the control value. In contrast, raising the pH(o) from 7.35 to 8.4 did not affect significantly the activation midpoint and current amplitude. Application of Zn(2+) in the concentration range from 100 microM to 1 mM at pH(o)=6.4 slowed additionally the activation rate, shifted the activation midpoint by about 20 mV towards positive membrane potentials and reduced the current amplitude in a concentration-dependent manner. The total effect exerted by Zn(2+) and protons at pH(o) = 6.4 was more significant than the effect exerted by Zn alone. Both the magnitude of the shift and the degree of current inhibition by Zn(2+) were independent on pH(o) in the range from 6.4 to 8.4. The data might suggest that the effects exerted by protons and zinc ions occur independently on each other and probably involve different mechanisms. Changing the holding potential from -90 mV to -60 mV at pH(o)=7.35 abolished the Zn(2+)-induced inhibition of the current amplitudes at concentrations below 300 microM. At pH(o)=6.4 the total inhibition caused by Zn(2+) and protons was also diminished, however, a significant reduction was observed at 100 microM concentration. In contrast, changing the holding potential did not change the Zn(2+)- and proton-induced shift of the activation midpoint. Altogether, obtained data suggest that extracellular protons exert the modulatory effects that are additive to the effects exerted by Zn(2+) on the channels. Possible physiological significance of these additive effects is discussed.
在本研究中，我们应用全细胞膜片钳技术来研究细胞外pH值（pH(o)）对锌离子（Zn(2+)）对人淋巴细胞中表达的电压门控钾通道Kv1.3的调节作用的影响。获得的数据表明，将pH(o)从7.35降低到6.4会显著减慢电流激活速率，使激活中点向正膜电位方向移动约16 mV，并将电流幅度降低至对照值的约0.55。相反，将pH(o)从7.35提高到8.4对激活中点和电流幅度没有显著影响。在pH(o)=6.4时，应用浓度范围为100 microM至1 mM的Zn(2+)会进一步减慢激活速率，使激活中点向正膜电位方向移动约20 mV，并以浓度依赖的方式降低电流幅度。在pH(o)=6.4时，Zn(2+)和质子共同产生的总效应比单独的Zn(2+)效应更显著。Zn(2+)引起的激活中点的移动幅度和电流抑制程度在6.4至8.4的pH范围内均与pH(o)无关。这些数据可能表明，质子和锌离子的作用相互独立，可能涉及不同的机制。在pH(o)=7.35时，将钳制电位从-90 mV改变为-60 mV可消除浓度低于300 microM时Zn(2+)诱导的电流幅度抑制。在pH(o)=6.4时，Zn(2+)和质子引起的总抑制也会减弱，然而，在100 microM浓度时观察到显著降低。相反，改变钳制电位不会改变Zn(2+)和质子引起的激活中点的移动。总之，获得的数据表明，细胞外质子发挥的调节作用与Zn(2+)对通道的作用具有叠加性。讨论了这些叠加效应可能的生理意义。
