Busch A E, Herzer T, Wagner C A, Schmidt F, Raber G, Waldegger S, Lang F
Physiologisches Institut I, Eberhard-Karls-Universität Tübingen, Germany.
Mol Pharmacol. 1994 Oct;46(4):750-3.
cRNA encoding the human IsK protein was injected into Xenopus oocytes and the induced IsK channels were investigated using the two-microelectrode voltage-clamp method. Niflumic acid, mefenamic acid, flufenamic acid, and 4,4'-diisothiocyanatostilbene-2,2'- disulfonic acid, which are commonly used in Xenopus oocytes to suppress endogenous Ca(2+)-activated Cl- channels, were tested for their effects on IsK channels. At low concentrations (10 microM) all compounds increased IsK amplitude and decreased the rate of IsK deactivation. At 100 microM these compounds further decreased the rate of IsK deactivation, resulting in persistent activation of IsK, similar to what has been previously described for the action of organic cross-linkers on IsK. However, at 100 microM niflumic acid and flufenamic acid decreased the time-dependent outward current, whereas 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid and mefenamic acid caused an additional increase. When Cl- was completely substituted with gluconate, IsK had somewhat altered activation properties, but niflumic acid produced similar positive regulatory effects on IsK and shifted the voltage needed to evoke half-maximal IsK activation (V1/2) by about -20 mV. In summary, these compounds positively regulate IsK, presumably by stabilizing open IsK channels.
将编码人IsK蛋白的cRNA注射到非洲爪蟾卵母细胞中，并用双微电极电压钳法研究诱导产生的IsK通道。测试了在非洲爪蟾卵母细胞中常用于抑制内源性Ca(2+)激活的Cl-通道的氟尼辛、甲芬那酸、氟芬那酸和4,4'-二异硫氰酸芪-2,2'-二磺酸对IsK通道的影响。在低浓度（10 microM）时，所有化合物均增加IsK电流幅度并降低IsK失活速率。在100 microM时，这些化合物进一步降低IsK失活速率，导致IsK持续激活，类似于先前描述的有机交联剂对IsK的作用。然而，在100 microM时，氟尼辛和氟芬那酸降低了时间依赖性外向电流，而4,4'-二异硫氰酸芪-2,2'-二磺酸和甲芬那酸则导致额外增加。当Cl-完全被葡萄糖酸盐取代时，IsK的激活特性有所改变，但氟尼辛对IsK产生类似的正向调节作用，并使诱发半数最大IsK激活所需的电压（V1/2）向负方向移动约20 mV。总之，这些化合物可能通过稳定开放的IsK通道对IsK进行正向调节。
