Single delayed rectifier channels in frog atrial cells. Effects of beta-adrenergic stimulation

Biophys J. 1990 Apr;57(4):903-9. doi: 10.1016/S0006-3495(90)82610-2.

Abstract

The patch-clamp technique with two pipettes was used to record single delayed K+ channels (cell-attached electrode) and to control the potential and the composition of the intracellular compartment (whole-cell electrode). With 30 microM cAMP in the cell and physiological potassium concentrations inside and outside the patch, a channel carrying an outward current was characterized. Its open probability was very low and the channel was recorded in only 5% of patches under control conditions. Increasing intracellular cAMP increased the probability of finding a channel in a patch 10-fold. The channel had the characteristics expected of a delayed rectifier channel. The time-course of its ensemble average resembled the whole-cell current in the same cell. The current-voltage relationship exhibited inward rectification, with a slope conductance of 20 pS in the linear portion and a reversal potential close to EK. Both the open- and the closed-time distributions were described by the sum of two exponentials, suggesting a complicated gating scheme involving two closed states and two open states. The beta-adrenergic stimulation did not change the conductance of the channel, but increased its probability of opening.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Atrial Function
  • Cyclic AMP / pharmacology
  • Electric Conductivity
  • Electrophysiology / methods
  • Heart / physiology*
  • Heart Atria / drug effects
  • In Vitro Techniques
  • Isoproterenol / pharmacology*
  • Kinetics
  • Membrane Potentials / drug effects
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Probability
  • Rana catesbeiana
  • Receptors, Adrenergic, beta / physiology
  • Time Factors

Substances

  • Potassium Channels
  • Receptors, Adrenergic, beta
  • Cyclic AMP
  • Isoproterenol