AJP - Renal Physiology, Vol 264, Issue 3 565-F574, Copyright © 1993 by American Physiological Society

ARTICLES

Feedback regulation of Na channels in rat CCT. II. Effects of inhibition of Na entry

G. Frindt, R. B. Silver, E. E. Windhager and L. G. Palmer
Department of Physiology and Biophysics, Cornell University Medical College, New York, New York 10021.

Na channels in the apical membrane of the rat renal cortical collecting tubule were studied using the patch-clamp technique. Channel activity was monitored in cell-attached patches on tubules that were split open to expose the luminal surface. Channel number (N), open probability (Po), and single-channel currents (i) were measured at 37 degrees C during continuous superfusion of the tubule. Addition of amiloride (10 microM) or benzamil (0.5 microM) to the superfusate resulted in a twofold increase in the mean number of open channels (NPo) after 2 min. The effect closely paralleled an increase in i, presumably reflecting membrane hyperpolarization. The effects on both i and NPo reversed within 3 min after removal of amiloride. The increase in NPo was accounted for, at least in part, by an increase in Po. Several cellular events may contribute to this phenomenon. Channels could be activated directly by membrane hyperpolarization and by cell shrinkage, both of which are known to occur during acute administration of amiloride. In addition, benzamil elicited a 30% decrease in intracellular Ca compared with control levels as measured by fura-2 fluorescence. A comparable decrease observed after reducing extracellular Ca did not increase NPo. No changes in cell pH, measured with 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein fluorescence, were observed. The modulation of channel Po by the rate of Na entry into the cell will act as a feedback mechanism to maintain cellular ion homeostasis, and this may also serve to distribute Na reabsorption more evenly along the nephron.

This article has been cited by other articles:

				J. Lebowitz, B. An, R. S. Edinger, M. L. Zeidel, and J. P. Johnson Effect of altered Na+ entry on expression of apical and basolateral transport proteins in A6 epithelia Am J Physiol Renal Physiol, September 1, 2003; 285(3): F524 - F531. [Abstract] [Full Text] [PDF]

				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]

				L. Dijkink, A. Hartog, C. H. Van Os, and R. J. M. Bindels Modulation of aldosterone-induced stimulation of ENaC synthesis by changing the rate of apical Na+ entry Am J Physiol Renal Physiol, October 1, 2001; 281(4): F687 - F692. [Abstract] [Full Text] [PDF]

				E. Feraille and A. Doucet Sodium-Potassium-Adenosinetriphosphatase-Dependent Sodium Transport in the Kidney: Hormonal Control Physiol Rev, January 1, 2001; 81(1): 345 - 418. [Abstract] [Full Text] [PDF]

				J. Loffing, L. Pietri, F. Aregger, M. Bloch-Faure, U. Ziegler, P. Meneton, B. C. Rossier, and B. Kaissling Differential subcellular localization of ENaC subunits in mouse kidney in response to high- and low-Na diets Am J Physiol Renal Physiol, August 1, 2000; 279(2): F252 - F258. [Abstract] [Full Text] [PDF]

				W. Wang Regulation of the ROMK channel: interaction of the ROMK with associate proteins Am J Physiol Renal Physiol, December 1, 1999; 277(6): F826 - F831. [Abstract] [Full Text] [PDF]

				L. G. Palmer and G. Frindt Regulation of apical K channels in rat cortical collecting tubule during changes in dietary K intake Am J Physiol Renal Physiol, November 1, 1999; 277(5): F805 - F812. [Abstract] [Full Text] [PDF]

				M. S. Awayda Regulation of the epithelial Na+ channel by intracellular Na+ Am J Physiol Cell Physiol, August 1, 1999; 277(2): C216 - C224. [Abstract] [Full Text] [PDF]

				G. Schultheiss and H. Martens Ca-sensitive Na transport in sheep omasum Am J Physiol Gastrointest Liver Physiol, June 1, 1999; 276(6): G1331 - G1344. [Abstract] [Full Text] [PDF]

				N. L. Nakhoul, K. S. Hering-Smith, C. T. Gambala, and L. L. Hamm Regulation of sodium transport in M-1 cells Am J Physiol Renal Physiol, December 1, 1998; 275(6): F998 - F1007. [Abstract] [Full Text] [PDF]

				A. Dinudom, K. F. Harvey, P. Komwatana, J. A. Young, S. Kumar, and D. I. Cook Nedd4 mediates control of an epithelial Na+ channel in salivary duct cells by cytosolic Na+ PNAS, June 9, 1998; 95(12): 7169 - 7173. [Abstract] [Full Text] [PDF]

				H. Choe, H. Zhou, L. G. Palmer, and H. Sackin A conserved cytoplasmic region of ROMK modulates pH sensitivity, conductance, and gating Am J Physiol Renal Physiol, October 1, 1997; 273(4): F516 - F529. [Abstract] [Full Text] [PDF]