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在多种平滑肌上都已发现Ｃａ２＋激活Ｃｌ－通道。胞内游离钙升高是钙激活氯通道的必要条件。多种刺激剂诱导胞内钙库释放钙而同时激活钾通道［ＩＫ（Ｃａ）］和氯通道［ＩＣｌ（Ｃａ）］。平滑肌细胞上激活ＩＣｌ（Ｃａ）的［Ｃａ２＋］ｉ阈值因动物种属和组织差异而不同。用荧光指示剂直接测定大鼠门静脉平滑肌细胞上的［Ｃａ２＋］ｉ得出激活ＩＫ（Ｃａ）的最小［Ｃａ２＋］ｉ应大于７０～８０μｍｏｌ·Ｌ－１，比激活ＩＣｌ（Ｃａ）的最低浓度１８０μｍｏｌ·Ｌ－１要小，因此认为ＩＫ（Ｃａ）要比ＩＣｌ（Ｃａ）对［Ｃａ２＋］ｉ更敏感。胞外钙通过电压依赖性钙通道进入胞内，［Ｃａ２＋］ｉ升高也能激活氯通道。Ｇ蛋白与某些受体偶联激活胞内第二信使ＩＰ３而激活氯通道。钙激活氯通道的电导很小，从全细胞电流分析应小于１０ｐＳ。平滑肌细胞上的氯平衡电位（ＥＣｌ）正于静息膜电位，因此Ｃｌ－通道开放Ｃｌ－外流驱动膜电位向ＥＣｌ方向靠近，形成膜的去极化。Ｃａ２＋激活Ｃｌ－通道开放使细胞膜去极化并引起细胞的兴奋，这种通道在由激素或神经递质引起平滑肌细胞的兴奋过程中起重要作用。
Ca2 + has been found to activate Cl-channels on many types of smooth muscle. Elevated intracellular free calcium is a necessary condition for calcium to activate the chloride channel. Various stimulators induce intracellular calcium stores to release calcium while activating potassium channels [IK (Ca)] and chloride channels [ICl (Ca)]. The [Ca2 +] i threshold for activation of IC1 (Ca) on smooth muscle cells varies with animal species and tissue differences. Direct determination of [Ca2 +] i on rat portal vein smooth muscle cells with fluorescent indicator gave a minimum [Ca2 +] i of activated IK (Ca) greater than 70-80 μmol·L-1, which was lower than the lowest concentration of IC1 (Ca) · L-1 is smaller, so IK (Ca) is considered to be more sensitive to [Ca 2+] i than ICl (Ca). Extracellular calcium enters the cell via a voltage-dependent calcium channel, and an increase in [Ca2 +] i also activates the chloride channel. Coupling of the G protein to certain receptors activates the intracellular second messenger IP3 to activate the chloride channel. The conductance of calcium-activated chloride channels is small and should be less than 10 pS from whole-cell current analysis. The chloride balance potential (ECl) on smooth muscle cells is at resting membrane potential, so the Cl- channel opens Cl-outflow to drive the membrane potential towards the ECl direction, forming membrane depolarization. Ca2 + activates the opening of the Cl-channel to depolarize the cell membrane and cause cellular excitation which plays an important role in the excitation of smooth muscle cells by hormones or neurotransmitters.