Increased expression and activity of sodium channels in alveolar type II cells of hyperoxic rats

Academic Article

Abstract

  • We investigated the cellular and molecular events associated with the increase in sodium transport across the alveolar epithelium of rats exposed to hyperoxia (85% O2 for 7 days followed by 100% O2 for 4 days). Alveolar type II (ATII) cell RNA was isolated and probed with a cDNA for one of the rat colonic epithelial sodium channel subunits (αrENaC). The αrENaC mRNA (3.7-kb transcript) increased 3-fold in ATII cell RNA isolated from rats exposed to 85% O2 for 7 days and 6-fold after 4 days of subsequent exposure to 100% O2. In situ hybridization revealed increased expression of αrENaC mRNA transcripts in both airway and alveolar epithelial cells of hyperoxic rats. When immunostained with a polyclonal antibody to kidney sodium channel protein, ATII cells from hyperoxic rats exhibited a significant increase in the amount of immunogenic protein present in both the plasma membrane and the cytoplasm. When patched in the whole-cell mode, ATII cells from hyperoxic rats exhibited amiloride and 5-(N-ethyl-N-isopropyl)-2',4'-amiloride (EIPA)sensitive currents that were 100% higher compared with those obtained from air-breathing rats. Single-channel sodium currents (mean conductance of 25 pS) were seen in ATII cells patched in both the inside-out and cell- attached modes. The number and open probability of these channels increased significantly during exposure to hyperoxia. Exposure to sublethal hyperoxia up-regulated both αrENaC mRNA and the functional expression of sodium channels in ATII cells.
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Yue G; Russell WJ; Benos DJ; Jackson RM; Olman MA; Matalon S
  • Start Page

  • 8418
  • End Page

  • 8422
  • Volume

  • 92
  • Issue

  • 18