Single-channel properties of swelling-activated anion conductance in rat inner medullary collecting duct cells.

Single-channel properties of the volume-activated outwardly rectifying Cl- conductance of rat IMCD cells were studied in primary cultures by means of the patch-clamp technique in the whole cell and in the outside-out configuration. Measurements were performed by noise analysis and in single-channel recordings during voltage-induced current inactivation and reactivation and in long-lasting experiments at constant membrane voltages. Unitary conductances could be defined for the voltage range of -100 to -50 mV and between +50 and +120 mV and chord conductances of 34.1 and 76.6 pS, respectively, can be calculated. The overall current-to-voltage relationship very much resembles that of the macroscopic Cl- conductance and the open probability of the activated channel is close to unity (Po = 0.98-0.99). The channel exhibits many similarities to volume-activated outwardly rectifying Cl- channels found in other systems although certain species differences do exist.