Single delayed rectifier channels in frog atrial cells. Effects of beta-adrenergic stimulation.
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.
Duchatelle-Gourdon
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Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, GA 30322.
Hartzell
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HC
D000818:Animals; D016275:Atrial Function; D000242:Cyclic AMP / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011336:Probability; D011892:Rana catesbeiana; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D013997:Time Factors
D015221:Potassium Channels; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D007545:Isoproterenol