Ackerman M J, Wickman K D, Clapham D E
Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905.
J Gen Physiol. 1994 Feb;103(2):153-79. doi: 10.1085/jgp.103.2.153.
Xenopus oocytes are frequently utilized for in vivo expression of cellular proteins, especially ion channel proteins. A thorough understanding of the endogenous conductances and their regulation is paramount for proper characterization of expressed channel proteins. Here we detail a novel chloride current (ICl.swell) responsive to hypotonicity in Xenopus oocytes using the two-electrode voltage clamp technique. Reducing the extracellular osmolarity by 50% elicited a calcium-independent chloride current having an anion conductivity sequence identical with swelling-induced chloride currents observed in epithelial cells. The hypotonicity-activated current was blocked by chloride channel blockers, trivalent lanthanides, and nucleotides. G-protein, cAMP-PKA, and arachidonic acid signaling cascades were not involved in ICl.swell activation. ICl.swell is distinct from both stretch-activated nonselective cation channels and the calcium-activated chloride current in oocytes and may play a critical role in volume regulation in Xenopus oocytes.
非洲爪蟾卵母细胞经常被用于细胞蛋白尤其是离子通道蛋白的体内表达。对于正确表征所表达的通道蛋白而言，全面了解内源性电导及其调节至关重要。在此，我们使用双电极电压钳技术详细描述了非洲爪蟾卵母细胞中一种对低渗刺激有反应的新型氯离子电流（ICl.swell）。将细胞外渗透压降低50%会引发一种不依赖钙的氯离子电流，其阴离子传导序列与上皮细胞中观察到的肿胀诱导氯离子电流相同。低渗激活电流可被氯离子通道阻滞剂、三价镧系元素和核苷酸阻断。G蛋白、cAMP-PKA和花生四烯酸信号级联反应不参与ICl.swell的激活。ICl.swell既不同于牵张激活的非选择性阳离子通道，也不同于卵母细胞中的钙激活氯离子电流，可能在非洲爪蟾卵母细胞的体积调节中起关键作用。
