Evidence for the involvement of a K+ channel in isosmotic cell shrinking in vestibular dark cells.
Cell volume changes were measured in dark cells. Isosmotic addition of 21.4 mM K+, Rb+, Cs+, or NH4+ to a control solution containing 3.6 mM K+ caused piretanide-sensitive cell swelling (initial rate for K+, 0.100 +/- 0.005 microns/s; n = 119), suggesting dependence on the Na(+)-Cl(-)-K+ cotransporter. Subsequent isosmotic removal of 21.4 mM K+ caused piretanide-insensitive cell shrinking (initial rate, -0.104 +/- 0.005 microns/s; n = 119), which was inhibited by barium, lidocaine, quinidine, quinine, verapamil, and 4-aminopyridine but not tetraethylammonium (TEA) or glibenclamide, suggesting the involvement of K+ channel(s). Barium, lidocaine, quinine, quinidine, and 4-aminopyridine caused cell swelling in control solution (initial rate for barium, 0.011 +/- 0.004 microns/s; n = 6), suggesting that the K+ channel is also involved in efflux under control conditions. Cell shrinking was slowed by 21.4 mM extracellular K+, Rb+, or Cs+ but unaffected by Na+, Li+, TEA+, or NH4+ (all in the presence of piretanide and compared with N-methyl-D-glucamine), supporting the notion that the efflux mechanism is permeable to and/or inhibited by K+, Rb+, and Cs+. Cell shrinking was slowed by the presumed replacement of intracellular K+ by Cs+ but not by Rb+. Circumstantial evidence suggests that this putative K+ channel is present in the basolateral membrane. The physiological relevance of such a K+ channel might encompass regulatory volume decrease during K+ secretion.
Wangemann
P
P
Cell Physiology Laboratory, Boys Town National Research Hospital, Omaha, Nebraska 68131.
Shiga
N
N
Welch
C
C
Marcus
D C
DC
D000818:Animals; D002412:Cations / Q000378:metabolism / Q000494:pharmacology; D004232:Diuretics / Q000494:pharmacology; D007758:Ear, Inner / Q000166:cytology* / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D007477:Ions; D009995:Osmosis; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*
D002412:Cations; D004232:Diuretics; D007477:Ions; D015221:Potassium Channels; D011188:Potassium