Alveolar transepithelial potential difference and ion transport in adult rat lung

Abstract

The complex morphology of the mammalian lung complicates characterization of solute transport across the intact alveolar epithelium. We impaled the subpleural alveolar epithelium with microelectrodes and measured the transepithelial potential difference (PD) of the liquid-filled vascular-perfused left lobe of the rat lung. When the air space was filled entirely with Krebs-Ringer-bicarbonate, the PD was 4.7 mV (lumen negative). The PD was not affected significantly by agents that modify either Na+ or Cl- transport, but replacement of luminal Cl- with gluconate resulted in a fourfold hyperpolarization, a response also noted for large airways. When the airways were blocked by an immiscible nonconducting fluorocarbon, basal PD was not different from unblocked lobes (4.0 mV) but was inhibited 73% by luminal amiloride. Cl(-)-free Krebs-Ringer-bicarbonate blocked in the alveoli with fluorocarbon did not induce hyperpolarization. This result suggests that 1) Cl- permselectivity of the alveolar epithelium is less than that of large airway epithelium and 2) airway PD dominates the voltage across the liquid-filled lung, even when measurements are made from alveoli. When airways are blocked by fluorocarbon, the PD across the alveolar epithelium is largely dependent on Na+ flow through a path with amiloride-sensitive channels.

Cl-channel activation is necessary for stimulation of Na transport in adult alveolar epithelial cells

“…It has been previously shown that adrenergic agonists increase fluid absorption across the rat alveolar epithelium and that this increase is inhibited if the lungs are infused with amiloride (5,15,18). This result supports the idea that stimulation of amiloride-sensitive Na absorption establishes the necessary osmotic driving force required for fluid removal from the alveoli (3,6,7,14). The proposed mechanism to account for enhanced Na absorption is an increase in apical membrane Na permeability resulting from cAMPmediated increases in the open probability of amiloridesensitive Na channels.…”

Development of Salt and Water Transport across Airway and Alveolar Epithelia

“…63 Native tracheal epithelia of the larger mammalian species (dog, human, cow, horse, sheep, etc.) V te in rat alveoli is ∼5 mV, 71 and in rabbits is ∼1 mV. Welldifferentiated cultures of airway epithelium have cell heights and I sc 's that are similar to native epithelium.…”

Cellular processes involved in lung cancer cells exposed to direct current electric field

“…Therefore, further biological experimental verification could not be performed. For example, in a physiological experiment using adult rat lungs, the alveolar transepithelial potential difference was observed by a unique method for isolating intact alveolar epithelial cells from parallel pulmonary epithelia 84 . This type of research provides a solid physiological basis for investigating the mechanism by which electric fields affect cells.…”