Department of Physiology Anatomy & Development Biology, Monash University, Clayton, Victoria, Australia.
Br J Pharmacol. 2012 Apr;165(7):2389-408. doi: 10.1111/j.1476-5381.2011.01730.x.
Although atypical smooth muscle cells (SMCs) in the proximal renal pelvis are thought to generate the pacemaker signals that drive pyeloureteric peristalsis, their location and electrical properties remain obscure.
Standard patch clamp, intracellular microelectrode and immunohistochemistry techniques were used. To unequivocally identify SMCs, transgenic mice with enhanced yellow fluorescent protein (eYFP) expressed in cells containing α-smooth muscle actin (α-SMA) were sometimes used.
Atypical SMCs were distinguished from typical SMCs by the absence of both a transient 4-aminopyridine-sensitive K(+) current (I(KA) ) and spontaneous transient outward currents (STOCs) upon the opening of large-conductance Ca(2+) -activated K(+) (BK) channels. Many typical SMCs displayed a slowly activating, slowly decaying Cl(-) current blocked by niflumic acid (NFA). Immunostaining for K(V) 4.3 and ANO1/ TMEM16A Cl(-) channel subunits co-localized with α-SMA immunoreactive product predominately in the distal renal pelvis. Atypical SMCs fired spontaneous inward currents that were either selective for Cl(-) and blocked by NFA, or cation-selective and blocked by La(3+) . α-SMA(-) interstitial cells (ICs) were distinguished by the presence of a Xe991-sensitive K(V) 7 current, BK channel STOCs and Cl(-) selective, NFA-sensitive spontaneous transient inward currents (STICs). Intense ANO1/ TMEM16A and K(V) 7.5 immunostaining was present in Kit(-) α-SMA(-) ICs in the suburothelial and adventitial regions of the renal pelvis.
We conclude that K(V) 4.3(+) α-SMA(+) SMCs are typical SMCs that facilitate muscle wall contraction, that ANO1/ TMEM16A and K(V) 7.5 immunoreactivity may be selective markers of Kit(-) ICs and that atypical SMCs which discharge spontaneous inward currents are the pelviureteric pacemakers.
尽管近端肾盂中的非典型平滑肌细胞（SMC）被认为会产生驱动肾盂输尿管蠕动的起搏信号，但它们的位置和电特性仍不清楚。
使用标准的膜片钳、细胞内微电极和免疫组织化学技术。为了明确鉴定 SMC，有时使用在含有α-平滑肌肌动蛋白（α-SMA）的细胞中表达增强型黄色荧光蛋白（eYFP）的转基因小鼠。
非典型 SMC 与典型 SMC 的区别在于，当大电导钙激活钾（BK）通道打开时，它们既没有短暂的 4-氨基吡啶敏感钾（K(+)）电流（I(KA) ），也没有自发瞬时外向电流（STOCs）。许多典型的 SMC 显示出一种缓慢激活、缓慢衰减的氯离子（Cl(-)）电流，被尼氟灭酸（NFA）阻断。对 K(V) 4.3 和 ANO1/TMEM16A Cl(-)通道亚基的免疫染色与 α-SMA 免疫反应产物主要在远端肾盂中共同定位。非典型 SMC 产生自发性内向电流，这些电流要么对 Cl(-)有选择性，被 NFA 阻断，要么对阳离子有选择性，被 La(3+) 阻断。α-SMA(-)间质细胞（ICs）通过存在 Xe991 敏感的 K(V) 7 电流、BK 通道 STOCs 和 Cl(-)选择性、NFA 敏感的自发性瞬时内向电流（STICs）来区分。Kit(-)α-SMA(-)ICs 在肾盂的下尿路上皮和外膜区域中强烈表达 ANO1/TMEM16A 和 K(V) 7.5。
我们得出结论，K(V) 4.3(+)α-SMA(+)SMC 是促进肌壁收缩的典型 SMC，ANO1/TMEM16A 和 K(V) 7.5 免疫反应可能是 Kit(-)IC 的选择性标志物，而发出自发性内向电流的非典型 SMC 是肾盂输尿管的起搏细胞。
