Antidiuretic hormone-responding nonselective cation channel in distal nephron epithelium (A6).
Arginine vasotocin (AVT, 70 mU/ml) added from the basolateral side transiently activated a nonselective cation (NSC) channel with a single-channel conductance of 28.5 pS and almost identical selectivity for Na+ and K+ in the apical membrane of distal nephron cells (A6) cultured on permeable supports for 10-12 days in media containing 10% fetal bovine serum without supplemental aldosterone. The open probability (Po) of the NSC channel at the apical resting membrane potential in cell-attached patches was approximately 0.09 and increased when the apical membrane depolarized. The Po of the NSC channel was decreased by a rise in cytosolic Ca2+ concentration within a range of 30 nM-1 microM but not affected by cytosolic pH within a range of 6-8. The channel was activated by the application of negative pressure (10-60 cmH2O) into the patch pipette. Gadolinium (2 microM), an inhibitor of stretch-activated channels, decreased the Po by 40%. This blocking action of gadolinium was more effective after the channel was activated by stretch, i.e., 2 microM gadolinium decreased the Po by 70% when a negative pressure (60 cmH2O) was applied into the patch pipette. Amiloride (10 and 100 microM) showed a blocking action on the channel only when the NSC channel was activated by stretch.
Marunaka
Y
Y
Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
Tohda
H
H
Hagiwara
N
N
Nakahari
T
T
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005682:Gadolinium / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D009399:Nephrons / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D010812:Physical Stimulation; D014667:Vasopressins / Q000502:physiology*; D014668:Vasotocin / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D014667:Vasopressins; D000584:Amiloride; D005682:Gadolinium; D002118:Calcium; D014668:Vasotocin