Lomax R B, McNicholas C M, Lombès M, Sandle G I
Epithelial Membrane Research Centre, University of Manchester, Hope Hospital, Salford, United Kingdom.
Am J Physiol. 1994 Jan;266(1 Pt 1):G71-82. doi: 10.1152/ajpgi.1994.266.1.G71.
Aldosterone is a major regulator of Na(+)-absorptive and K(+)-secretory processes in the distal segment of mammalian colon. In this study, the distribution of aldosterone-sensitive cell types in isolated rat distal colon was determined using site-directed intracellular microelectrodes, specific Na(+)- and K(+)-channel blockers, and aldosterone-receptor binding techniques. Electrophysiological data indicated that aldosterone induced parallel apical membrane Na+ and K+ conductances, mainly in surface cells and to a significantly lesser degree in crypt cells. Scatchard analyses of aldosterone-receptor binding in cytosolic fractions revealed the maximum number of specific binding sites in whole mucosal homogenate and in the upper one-third and lower two-thirds of isolated crypt units to be 74.9 +/- 2.0, 59.8 +/- 2.4, and 59.3 +/- 3.2 fmol/mg protein, respectively, indicating the presence of aldosterone receptors in the crypt cell population. We conclude that in rat distal colon aldosterone-induced Na+ and K+ conductances (and by inference, electrogenic Na(+)-absorptive and K(+)-secretory processes) are located predominantly in the surface cell population and to a lesser extent in crypt cells, which also contain aldosterone receptors. This spectrum of aldosterone-induced Na+ and K+ conductances may reflect varying stages of differentiation along the surface cell-crypt cell axis.
醛固酮是哺乳动物结肠远端段钠吸收和钾分泌过程的主要调节因子。在本研究中，使用定点细胞内微电极、特异性钠通道和钾通道阻滞剂以及醛固酮受体结合技术，确定了分离的大鼠远端结肠中醛固酮敏感细胞类型的分布。电生理数据表明，醛固酮主要在表面细胞中诱导平行的顶端膜钠和钾电导，在隐窝细胞中的诱导程度明显较低。对细胞溶质部分中醛固酮受体结合的Scatchard分析显示，全黏膜匀浆以及分离的隐窝单位的上三分之一和下三分之二部分中特异性结合位点的最大数量分别为74.9±2.0、59.8±2.4和59.3±3.2 fmol/mg蛋白质，表明隐窝细胞群体中存在醛固酮受体。我们得出结论，在大鼠远端结肠中，醛固酮诱导的钠和钾电导（以及由此推断的电源性钠吸收和钾分泌过程）主要位于表面细胞群体中，在隐窝细胞中的程度较小，而隐窝细胞中也含有醛固酮受体。醛固酮诱导的钠和钾电导的这种分布可能反映了沿表面细胞-隐窝细胞轴不同的分化阶段。
