Chloride channels in the apical membrane of a distal nephron A6 cell line.
In this report, single-channel recording methods were used to determine whether there are Cl- conductive pathways in the apical membrane of cultured renal distal nephron cells (A6). Two different types of single Cl- channels were observed. In cell-attached patches, one had a unit conductance of 3 pS, whereas the unit conductance of the other was 8 pS. In cell-attached patches, the currents associated with the 3-pS Cl- channel outwardly rectified, whereas the current voltage relationship for the 8-pS Cl-channel was linear. The 3-pS Cl- channel has one open and one closed state; the 8-pS Cl- channel has one open and two closed states. The open probability of the 3-pS Cl- channel was voltage dependent (increasing with depolarization of the membrane) but even at very depolarized potentials (+140 mV) remained small (always less than 0.1). On the other hand, the open probability of the 8-pS Cl- channel was large (approximately 0.8) and voltage independent. The closing rate of the 3-pS Cl- channel was decreased when the patch membrane was depolarized, whereas the opening rate was increased. In contrast, the closing rate of the 8-pS Cl- channel decreased with depolarization, but the opening rates were voltage independent. The outward rectification of the 3-pS channel was markedly reduced in inside-out patches when high calcium concentrations (10-800 microM) were present on the intracellular surface. The open probability of the 3-pS Cl- channel is increased by membrane permeable analogues of adenosine 3',5'-cyclic monophosphate primarily by decreasing the mean closed time.
Marunaka
Y
Y
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
Eaton
D C
DC
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism* / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology*; D008962:Models, Theoretical; D009399:Nephrons / Q000502:physiology; D011336:Probability
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D003994:Bucladesine; D000242:Cyclic AMP; D002118:Calcium