Rajendran V M, Singh S K, Geibel J, Binder H J
Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA.
Am J Physiol. 1998 Feb;274(2):G424-9. doi: 10.1152/ajpgi.1998.274.2.G424.
Two distinct colonic H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) isoforms can be identified in part on the basis of their sensitivity to ouabain. The colonic H(+)-K(+)-ATPase alpha-subunit (HKc alpha) was recently cloned, and its message and protein are present in surface (and the upper 20% of crypt) cells in the rat distal colon. These studies were performed to establish the spatial distribution of the ouabain-sensitive and ouabain-insensitive components of both H(+)-K(+)-ATPase activity in apical membranes prepared from surface and crypt cells and K(+)-dependent intracellular pH (pHi) recovery from an acid load both in isolated perfused colonic crypts and in surface epithelial cells. Whereas H(+)-K(+)-ATPase activity in apical membranes from surface cells was 46% ouabain sensitive, its activity in crypt apical membranes was 96% ouabain sensitive. Similarly, K(+)-dependent pHi recovery in isolated crypts was completely ouabain sensitive, whereas in surface cells K(+)-dependent pHi recovery was insensitive to ouabain. These studies provide compelling evidence that HKc alpha encodes the colonic ouabain-insensitive H(+)-K(+)-ATPase and that a colonic ouabain-sensitive H(+)-K(+)-ATPase isoform is present in colonic crypts and remains to be cloned and identified.
可以根据两种不同的结肠H(+)-K(+)-三磷酸腺苷酶（H(+)-K(+)-ATP酶）亚型对哇巴因的敏感性对其进行部分鉴定。结肠H(+)-K(+)-ATP酶α亚基（HKcα）最近已被克隆，其信使核糖核酸和蛋白质存在于大鼠远端结肠的表面（以及隐窝上部20%）细胞中。进行这些研究是为了确定从表面和隐窝细胞制备的顶端膜中H(+)-K(+)-ATP酶活性的哇巴因敏感和哇巴因不敏感成分的空间分布，以及在分离的灌注结肠隐窝和表面上皮细胞中从酸负荷中恢复的钾依赖性细胞内pH（pHi）。表面细胞顶端膜中的H(+)-K(+)-ATP酶活性对哇巴因敏感的比例为46%，而其在隐窝顶端膜中的活性对哇巴因敏感的比例为96%。同样，分离的隐窝中钾依赖性pHi的恢复对哇巴因完全敏感，而在表面细胞中，钾依赖性pHi的恢复对哇巴因不敏感。这些研究提供了令人信服的证据，表明HKcα编码结肠中对哇巴因不敏感的H(+)-K(+)-ATP酶，并且结肠中存在一种对哇巴因敏感的H(+)-K(+)-ATP酶亚型，有待克隆和鉴定。
