Ion channels activated by swelling of Madin Darby canine kidney (MDCK) cells.
According to previous studies hyposmotic swelling of Madin Darby Canine Kidney (MDCK) cells leads to a marked decrease of cell membrane resistance. The present study has been performed to identify the underlying ion channels using the patch-clamp technique: reduction of extracellular osmolarity to 230 mmol/liter leads to a transient activation of K+ channels and a sustained activation of anion channels. The K+ channels are inwardly rectifying with a single-channel slope conductance of 56 +/- 3 pS at -50 mV (cell negative) and of 29 +/- 2 pS at 0 mV PD across the patch (150 mmol/liter K+ in pipette). The same channels are activated by an increase of intracellular calcium activity, as shown previously. The anion channels display a single-channel slope conductance of 41 +/- 4 pS at -50 mV (cell negative) and of 25 +/- 3 pS at 0 mV PD across the patch (150 mmol/liter Cl- in pipette). The channel is anion selective and conducts both bicarbonate and chloride with a preference for bicarbonate. Its open probability is not affected by changing intracellular calcium from 0.1-10 mumol/liter. The channels observed explain the effects of cell swelling on PD, ion selectivity and resistance of the cell membrane in MDCK cells.
Weiss
H
H
Institute for Physiology, University of Innsbruck, Austria.
Lang
F
F
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002412:Cations; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D004285:Dogs; D004553:Electric Conductivity; D015640:Ion Channel Gating; D008565:Membrane Proteins / Q000378:metabolism*; D008839:Microelectrodes; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000378:metabolism*
D001639:Bicarbonates; D002412:Cations; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D015221:Potassium Channels