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Updated: Aug 8, 2026
Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes
Published on: March 12, 2013
Swelling-induced chloride-sensitive current in canine atrial cells revealed by whole-cell patch-clamp method
1Department of Pharmacology, Columbia University, New York, NY 10032.
Insights
Canine atrial cells do not exhibit isoproterenol-induced chloride currents. Instead, cell swelling during patch-clamp experiments activates a chloride current, which isoproterenol can then enhance.
Area of Science:
- Cardiology
- Electrophysiology
- Ion Channels
Background:
- Isoproterenol-induced chloride currents are found in guinea pig and rabbit ventricular myocytes but not canine ventricular cells.
- This study investigates the presence of such currents in canine atrial cells.
Purpose of the Study:
- To determine if canine atrial cells possess an isoproterenol-induced chloride current.
- To characterize the properties of any detected current and its relationship to experimental conditions.
Main Methods:
- Whole-cell and perforated patch-clamp techniques were used on canine atrial cells.
- Potassium currents were blocked with cesium.
- Experiments involved varying extracellular chloride concentration and osmolarity, and using anthracene-9-carboxylic acid.
Main Results:
- No direct isoproterenol-induced chloride current was detected.
- A spontaneously activating, outwardly rectifying chloride current developed over time in whole-cell recordings, linked to cell swelling.
- This swelling-induced current was sensitive to extracellular chloride and partially blocked by anthracene-9-carboxylic acid.
- Isoproterenol could enhance the amplitude of the swelling-induced current.
- Cell swelling and current development were prevented by adding mannitol or using low osmolarity solutions in perforated patch recordings.
Conclusions:
- Canine atrial cells do not exhibit a direct isoproterenol-induced chloride current.
- Cell swelling during patch-clamp recordings activates a distinct chloride current in these cells.
- This swelling-activated chloride current, which can be modulated by isoproterenol, may have implications for cardiac electrophysiology.
Abstract:
An isoproterenol-induced chloride current has been detected in ventricular myocytes from guinea pig and rabbit but has not been found in canine ventricular cells. This investigation was undertaken to determine whether canine atrial cells possessed such a current. Steady-state currents were examined with potassium currents blocked by cesium. In whole-cell patch-clamp experiments, an isoproterenol-induced chloride current could not be detected shortly after patch rupture. However, whole-cell current in the absence of isoproterenol increased over time after patch rupture. The spontaneously activating steady-state current was outwardly rectifying with a reversal potential of approximately -25 mV. The current that developed over time was sensitive to variation in extracellular chloride concentration and was partially blocked by anthracene-9-carboxylic acid. Isoproterenol could enhance the amplitude of this current once it developed. Although isosmotic pipette filling and extracellular solutions were used, cell swelling was found to be the cause of the increase in whole-cell conductance that was observed during whole-cell patch-clamp experiments. The development of the current and the associated cell swelling could be prevented with the addition of 50-75 mM mannitol to the extracellular solution. The current could be observed in perforated patch recordings with nystatin when extracellular osmolarity was low (221 mosm/kg) but not when the extracellular solution was isosmotic (293 mosm/kg). Cardiac chloride currents have the potential to depolarize the resting membrane potential and cause abnormal automaticity. Chloride currents can also decrease the refractory period through a reduction in action potential duration.(ABSTRACT TRUNCATED AT 250 WORDS)
