Cellular effects of beta-adrenergic and of cAMP stimulation on potassium transport in rat alveolar epithelium

Pflugers Arch. 1989 Jul;414(3):340-5. doi: 10.1007/BF00584636.

Abstract

Alveolar fluid absorption is greatly enhanced by cAMP and by beta-adrenergic agonists via an increase in Na+ transport. Little is known about K+ homeostasis under these circumstances. We studied K+ transport across alveolar epithelium in isolated perfused rat lungs stimulated either by dibutyryl-cAMP or isoproterenol. K+ fluxes and the apparent permeability of 86Rb across the epithelium (alveoli to plasma) were interpreted according to a model involving two types of cells, B and L, distinguished by the location of Na+-K+-ATPases (basal and luminal). Water is considered to be absorbed by B cells in a solute-coupled process energized by a basolateral Na+-K+-ATPase that is stimulated by isoproterenol and cAMP. K+ transport out of the alveoli is due to the activity of a Na+-K+-ATPase located in the apical membrane of L cells. In the present study net transport rate of K+ was -0.5 +/- 0.15 nmol/s, n = 20 (out of alveoli) in control conditions. When the epithelium was stimulated by dibutyryl-cAMP (10(-4) mol/l) net absorption of K+ reversed to net 'secretion' into alveoli (3.2 +/- 0.31 nmol/s), fluid absorption was not stimulated. K+ 'secretion' was abolished by apical Ba2+, indicating it was due to opening of apical K+ channels. Basolateral ouabain reversed net K+ 'secretion' to net absorption indicating that K+ entry into alveoli was dependent on activity of B cell basolateral Na+-K+-ATPase (masking simultaneous K+ removal by apical L cell Na+-K+-pump). When larger concentrations of dibutyryl-cAMP (10(-3) mol/l) or when isoproterenol were used to stimulate the epithelium there was a tripling of fluid absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Agonists / pharmacology*
  • Animals
  • Barium / pharmacology
  • Cell Membrane / drug effects
  • Cell Membrane / physiology
  • Cell Membrane / ultrastructure
  • Cell Membrane Permeability / drug effects
  • Cyclic AMP / pharmacology*
  • Epithelial Cells
  • Epithelium / drug effects
  • Epithelium / metabolism
  • Homeostasis
  • Isoproterenol / pharmacology
  • Male
  • Ouabain / pharmacology
  • Potassium / metabolism
  • Potassium / pharmacokinetics*
  • Pulmonary Alveoli / cytology*
  • Pulmonary Alveoli / drug effects
  • Pulmonary Alveoli / metabolism
  • Rats
  • Receptors, Adrenergic, beta / drug effects
  • Rubidium Radioisotopes
  • Second Messenger Systems

Substances

  • Adrenergic beta-Agonists
  • Receptors, Adrenergic, beta
  • Rubidium Radioisotopes
  • Barium
  • Ouabain
  • Cyclic AMP
  • Isoproterenol
  • Potassium