Delayed activation of cardiac swelling-induced chloride current after step changes in cell size

A lag phase has been reported for the activation of cardiac swelling-induced chloride currents. Prior demonstrations of this lag used methods that produce gradual changes in cell size, making interpretation and quantification of the time course problematic.

Isolated dog atrial cells were studied using the whole cell, patch clamp technique. Step changes in cell size were produced by application of transient pulses of positive pressure, and the time course for activation of the swelling-induced chloride current was observed. There was a distinct temporal dissociation between size changes and current activation that was temperature sensitive. Activation half-times were 98 +/- 31 seconds and 586 +/- 112 seconds at 36 degrees C and room temperature, respectively. Swelling-induced chloride currents were evoked in a higher percentage of cells at 36 degrees C (83%) compared with room temperature (50%).

Cardiac swelling-induced chloride current activates with a distinct lag after step changes in cell size. The activation time course is temperature sensitive. These observations are consistent with the notion that signal transduction events, and not simply membrane stretch, are required for the activation of cardiac swelling-induced chloride current.