Aldosterone-induced apical Na+ and K+ conductances are located predominantly in surface cells in rat distal colon.

Academic Article

Abstract

  • 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.
  • Published In

    Keywords

  • Aldosterone, Animals, Cell Membrane, Colon, Electric Conductivity, Electrophysiology, In Vitro Techniques, Male, Microelectrodes, Potassium, Rats, Rats, Sprague-Dawley, Receptors, Mineralocorticoid, Sodium
  • Digital Object Identifier (doi)

    Author List

  • Lomax RB; McNicholas CM; Lomb├Ęs M; Sandle GI
  • Start Page

  • G71
  • End Page

  • G82
  • Volume

  • 266
  • Issue

  • 1 Pt 1