Chloride currents of single mitochondria-rich cells of toad skin epithelium.
1. Mitochondria-rich (MR) cells in free suspension were obtained by collagenase and trypsin treatments of toad skin epithelium and studied by whole-cell voltage clamp and membrane current fluctuation analysis. 2. Cells studied with a 100 microM amiloride and 5 mM Ba2+ Ringer solution on the outside and 10 mM Cs+ in the pipette generated large membrane currents with reversal potentials varying in a Nernstian way with pipette [Cl-]. 3. The membrane chloride currents were activated in excess of Goldman-Hodgkin-Katz rectification by cell depolarization and clamping to positive cell potentials (VC). The resulting Cl- permeability was presented as an S-shaped function of membrane potential with half-maximal activation in the range 0 mV < VC < 50 mV. 4. The power density spectrum of Cl- current fluctuations could be fitted with a single Lorentzian component with a corner frequency, fc, of 34.9 +/- 2.6 Hz, and a low frequency asymptote, S(o), or 14.6 +/- 1.3 pA2 s per cell (mean +/- S.E.M.; VC = 25 mV, ECl = 0 mV, n = 6). 5. The lower-limit single channel conductance, gamma Cl(1 - Po), was 128 +/- 9 pS (VC = 25 mV, n = 6), where Po is the open channel probability. With Po = 0.5, this result indicates that Cl- channels of large unitary conductance (200-300 pS) are present in the mitochondria-rich cell membrane.
August Krogh Institute, University of Copenhagen, Denmark.
E H
EH
Larsen
B J
BJ
Harvey
D000818:Animals; D002023:Bufo bufo; D002462:Cell Membrane / Q000502:physiology; D002586:Cesium / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000502:physiology*; D012879:Skin Physiological Phenomena; D013997:Time Factors
D018118:Chloride Channels; D002712:Chlorides; D002586:Cesium