Liao Tianjiang, Wang Ling, Halm Susan Troutman, Lu Luo, Fyffe Robert E W, Halm Dan R
Dept. of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, USA.
Am J Physiol Cell Physiol. 2005 Sep;289(3):C564-75. doi: 10.1152/ajpcell.00561.2004. Epub 2005 Apr 20.
The cellular mechanism for Cl(-) and K(+) secretion in the colonic epithelium requires K(+) channels in the basolateral and apical membranes. Colonic mucosa from guinea pig and rat were fixed, sectioned, and then probed with antibodies to the K(+) channel proteins K(V)LQT1 (Kcnq1) and minK-related peptide 2 (MiRP2, Kcne3). Immunofluorescence labeling for Kcnq1 was most prominent in the lateral membrane of crypt cells in rat colon. The guinea pig distal colon had distinct lateral membrane immunoreactivity for Kcnq1 in crypt and surface cells. In addition, Kcne3, an auxiliary subunit for Kcnq1, was detected in the lateral membrane of crypt and surface cells in guinea pig distal colon. Transepithelial short-circuit current (I(sc)) and transepithelial conductance (G(t)) were measured for colonic mucosa during secretory activation by epinephrine (EPI), prostaglandin E(2) (PGE(2)), and carbachol (CCh). HMR1556 (10 microM), an inhibitor of Kcnq1 channels (Gerlach U, Brendel J, Lang HJ, Paulus EF, Weidmann K, Brüggemann A, Busch A, Suessbrich H, Bleich M, and Greger R. J Med Chem 44: 3831-3837, 2001), partially (approximately 50%) inhibited Cl(-) secretory I(sc) and G(t) activated by PGE(2) and CCh in rat colon with an IC(50) of 55 nM, but in guinea pig distal colon Cl(-) secretory I(sc) and G(t) were unaltered. EPI-activated K(+)-secretory I(sc) and G(t) also were essentially unaltered by HMR1556 in both rat and guinea pig colon. Although immunofluorescence labeling with a Kcnq1 antibody supported the basolateral membrane presence in colonic epithelium of the guinea pig as well as the rat, the Kcnq1 K(+) channel is not an essential component for producing Cl(-) secretion. Other K(+) channels present in the basolateral membrane presumably must also contribute directly to the K(+) conductance necessary for K(+) exit during activation of Cl(-) secretion in the colonic mucosa.
结肠上皮细胞中氯离子(Cl⁻)和钾离子(K⁺)分泌的细胞机制需要在基底外侧膜和顶端膜中存在钾离子通道。将豚鼠和大鼠的结肠黏膜固定、切片,然后用针对钾离子通道蛋白K(V)LQT1(Kcnq1)和微小相关肽2(MiRP2,Kcne3)的抗体进行检测。在大鼠结肠隐窝细胞的侧膜中,Kcnq1的免疫荧光标记最为明显。豚鼠远端结肠的隐窝细胞和表面细胞的侧膜对Kcnq1有明显的免疫反应性。此外,在豚鼠远端结肠的隐窝细胞和表面细胞的侧膜中检测到了Kcnq1的辅助亚基Kcne3。在肾上腺素(EPI)、前列腺素E₂(PGE₂)和卡巴胆碱(CCh)刺激分泌时,测量结肠黏膜的跨上皮短路电流(I(sc))和跨上皮电导(G(t))。HMR1556(10微摩尔)是一种Kcnq1通道抑制剂(Gerlach U,Brendel J,Lang HJ,Paulus EF,Weidmann K,Brüggemann A,Busch A,Suessbrich H,Bleich M,和Greger R。J Med Chem 44:3831 - 3837,2001),它部分(约50%)抑制PGE₂和CCh在大鼠结肠中激活的氯离子分泌I(sc)和G(t),IC₅₀为55纳摩尔,但在豚鼠远端结肠中,氯离子分泌I(sc)和G(t)未改变。在大鼠和豚鼠结肠中,HMR1556对EPI激活的钾离子分泌I(sc)和G(t)也基本没有影响。尽管用Kcnq1抗体进行的免疫荧光标记支持在豚鼠和大鼠结肠上皮细胞的基底外侧膜中存在Kcnq1,但Kcnq1钾离子通道不是产生氯离子分泌的必需成分。基底外侧膜中存在的其他钾离子通道大概也必须直接参与结肠黏膜氯离子分泌激活过程中钾离子外流所需的钾离子电导。