Davidson J L, Kehl S J
Department of Physiology, University of British Columbia, Vancouver, Canada.
Can J Physiol Pharmacol. 1995 Jan;73(1):36-42. doi: 10.1139/y95-005.
We studied the effects of Zn2+ and Cd2+ on the behaviour of IK(f), a transient outward potassium current in acutely dissociated melanotrophs of the pars intermedia of the rat pituitary gland. Micromolar concentrations of external Cd2+ or Zn2+ caused parallel and nearly equal rightward shifts along the voltage axis of the activation and steady-state inactivation curves for IK(f). The KD for the half-maximal shift of the activation curve was 278 microM for Cd2+ and 93 microM for Zn2+; the maximal shifts of the activation curve were 32.5 and 34 mV, for Cd2+ and Zn2+, respectively. The times to half-activation and half-inactivation were shifted rightward by 30-60 mV in both 500 microM Cd2+ and 500 microM Zn2+. We suggest that Cd2+ and Zn2+ interact specifically with a binding site on or electrically close to the IK(f) channel and in so doing modify the electric field "seen" by the voltage sensors.
我们研究了锌离子（Zn2+）和镉离子（Cd2+）对大鼠垂体中间部急性分离的黑素细胞中瞬时外向钾电流IK(f)行为的影响。微摩尔浓度的细胞外镉离子（Cd2+）或锌离子（Zn2+）使IK(f)的激活曲线和稳态失活曲线沿电压轴平行且几乎等幅向右移动。镉离子（Cd2+）使激活曲线半最大移动的解离常数（KD）为278微摩尔，锌离子（Zn2+）为93微摩尔；镉离子（Cd2+）和锌离子（Zn2+）使激活曲线的最大移动分别为32.5和34毫伏。在500微摩尔镉离子（Cd2+）和500微摩尔锌离子（Zn2+）中，半激活时间和半失活时间均向右移动30 - 60毫伏。我们认为，镉离子（Cd2+）和锌离子（Zn2+）与IK(f)通道上或在电学上与之接近的一个结合位点特异性相互作用，进而改变电压感受器所“感知”的电场。
