尼氟灭酸通过钙库钙释放引起豚鼠耳蜗螺旋动脉平滑肌细胞超极化

本研究旨在观察氯离子通道阻断剂尼氟灭酸（niflumic acid，NFA）引起豚鼠耳蜗螺旋动脉平滑肌细胞产生超极化的机制。以豚鼠为实验动物，运用细胞内微电极和全细胞膜片钳记录技术，观察NFA和其它药物对急性分离的耳蜗螺旋动脉平滑肌细胞的作用。结果显示：NFA、indanyloxyacetic acid94（LAh-94）和diSOdium4，4’-diisothiocyanatostilbene-2，2’-disulfonate（DIDS）可使低静息膜电位的细胞产生超极化，但对高静息膜电位的细胞无明显作用。低静息膜电位细胞的平均静息电位为（-42．47±1．38）mV（n=24），100μmol／LNFA、10μmol／LIAA-94和200μmol／LDIDS分别使细胞超极化至（13．7±4．3）mV=9，P〈0．01），（11．4±4．2）mV（n=7，P〈0．01）和（12．3±3．7）mV（n=8，P〈0．01），这种氯离子通道阻断剂引起细胞超极化反应的效应呈浓度依赖性。NFA引起的超极化和外向电流几乎完全被100nmol／L iberiotoxin、100nmol／L charybdotoxin、10mmol／L tetraethylammonium、50μmol／LBAPTA—AM、10μmol／Lryanodine和0．1-10mmol／Lcaffeine阻断，但不能被100μmol／Lnifedipine、100μmol／LCdCI，和无Ca^2＋灌流外液阻断。结果捉示：氯离_了通道的阻断剂NFA可通过平滑肌细胞内钙库的钙释放增加细胞内钙，进而激活钙依赖的钾通道，产生耳蜗螺旋动脉平滑肌细胞的超极化反应。

Niflumic acid hyperpolarizes the smooth muscle cells by opening BK_(Ca) channels through ryanodine-sensitive Ca~(2+) release in spiral modiolar artery

The mechanism by which niflumic acid(NFA),a C1-channel antagonist,hyperpolarizes the smooth muscle cells(SMCs)of cochlear spiral modiolar artery(SMA)was explored.Guinea pigs were used as subjects and perforated patch clamp and intracellular recording technique were used to observe NFA-induced response of SMC in the acutely isolated SMA preparation.The results showed that bath application of NFA.indanyloxyacetic acid 94(IAA-94)and disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate(DIDS)caused hyperpolarization and evoked outward currents in all cells at low resting potential(RP),but had no effects in cells at high RP.In the low RP SMCs,the average RP was about(-42.47±1.38)mV(n=24).Application of NFA(100μmol/L),IAA-94(10μmol/L)and DIDS (200 μmol/L)shifted the RP to(13.7±4.3)mV(n=9,P<0.01),(11.4±4.2)mV(n=.7,P<0.01)and(12.3±3.7)mV(n=8,P<0.01),respectively.These drug-induced responses were in a concentration-dependent manner.NFA-induced hyperpolarization and outward current were almost blocked by charybdotoxin(100 nmol/L),iberiotoxin(100 nmol/L),tetraethylammonium(10 retool/L),BAPTA-AM(50 μmol/L),ryanodine(10μmol/L)andcaffeine(0.1-10mmol/L),respectively,but not by nifedipine(100μmol/L),CdC12(100μmol/L)andCa2+-free medium.It is concluded that NFA induces a release of intracellular calcium from the Ca2+ stores and the released intracellular calcium in turn causes concentration-dependent and reversible hyperpolarization and evokes outward currents in the SMCs of the cochlear SMA via activation of the Ca2+-activated potassium channels.