| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Medicine and Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
The hypothesis that the intracellular Na+ concentration ([Na+]i) is a regulator of the epithelial Na+ channel (ENaC) was tested with the Xenopus oocyte expression system by utilizing a dual-electrode voltage clamp. [Na+]i averaged 48.1 ± 2.2 meq (n = 27) and was estimated from the amiloride-sensitive reversal potential. [Na+]i was increased by direct injection of 27.6 nl of 0.25 or 0.5 M Na2SO4. Within minutes of injection, [Na+]i stabilized and remained elevated at 97.8 ± 6.5 meq (n = 9) and 64.9 ± 4.4 (n = 5) meq 30 min after the initial injection of 0.5 and 0.25 M Na2SO4, respectively. This increase of [Na+]i caused a biphasic inhibition of ENaC currents. In oocytes injected with 0.5 M Na2SO4 (n = 9), a rapid decrease of inward amiloride-sensitive slope conductance (gNa) to 0.681 ± 0.030 of control within the first 3 min and a secondary, slower decrease to 0.304 ± 0.043 of control at 30 min were observed. Similar but smaller inhibitions were also observed with the injection of 0.25 M Na2SO4. Injection of isotonic K2SO4 (70 mM) or isotonic K2SO4 made hypertonic with sucrose (70 mM K2SO4-1.2 M sucrose) was without effect. Injection of a 0.5 M concentration of either K2SO4, N-methyl-D-glucamine (NMDG) sulfate, or 0.75 M NMDG gluconate resulted in a much smaller initial inhibition (<14%) and little or no secondary decrease. Thus increases of [Na+]i have multiple specific inhibitory effects on ENaC that can be temporally separated into a rapid phase that was complete within 2-3 min and a delayed slow phase that was observed between 5 and 30 min.
epithelial sodium channel; Xenopus oocytes; inhibition; autoregulation; intracellular sodium concentration
This article has been cited by other articles:
|
|
 |
|
  M. S. Awayda, J. D. Platzer, R. L. Reger, and A. Bengrine Role of PKCalpha in feedback regulation of Na+ transport in an electrically tight epithelium Am J Physiol Cell Physiol, October 1, 2002; 283(4): C1122 - C1132. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. L. Nakhoul, K. S. Hering-Smith, S. M. Abdulnour-Nakhoul, and L. L. Hamm Ammonium interaction with the epithelial sodium channel Am J Physiol Renal Physiol, September 1, 2001; 281(3): F493 - F502. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. M. Satlin, S. Sheng, C. B. Woda, and T. R. Kleyman Epithelial Na+ channels are regulated by flow Am J Physiol Renal Physiol, June 1, 2001; 280(6): F1010 - F1018. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Jovov, A. Tousson, H.-L. Ji, D. Keeton, V. Shlyonsky, P.-J. Ripoll, C. M. Fuller, and D. J. Benos Regulation of Epithelial Na+ Channels by Actin in Planar Lipid Bilayers and in the Xenopus Oocyte Expression System J. Biol. Chem., December 31, 1999; 274(53): 37845 - 37854. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Dinudom, K. F. Harvey, P. Komwatana, C. N. Jolliffe, J. A. Young, S. Kumar, and D. I. Cook Roles of the C Termini of alpha -, beta -, and gamma -Subunits of Epithelial Na+ Channels (ENaC) in Regulating ENaC and Mediating Its Inhibition by Cytosolic Na+ J. Biol. Chem., April 20, 2001; 276(17): 13744 - 13749. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
