HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by MacLeod, R. J. Articles by Hamilton, J. R. Search for Related Content PubMed PubMed Citation Articles by MacLeod, R. J. Articles by Hamilton, J. R. Social Bookmarking                      What's this?

Volume 271, Number 38, Issue of September 20, 1996 pp. 23138-23145
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.

---

Activation of Na⁺/H⁺ Exchange Is Required for Regulatory Volume Decrease after Modest ``Physiological'' Volume Increases in Jejunal Villus Epithelial Cells

(Received for publication, April 16, 1996, and in revised form, July 3, 1996)

From the Department of Pediatrics, McGill University, Montreal Children's Hospital Research Institute, Montreal, Quebec H3H 1P3, Canada

Epithelial cell volume increases that occur because of the uptake of Na⁺-cotransported solutes or hypotonic dilution are followed by a regulatory volume decrease (RVD) due to the activation of K⁺ and Cl channels. We studied the relationship of Na⁺/H⁺ exchange (NHE) to this RVD in suspended guinea pig jejunal villus cells, using electronic sizing to measure cell volume changes and fluorescent spectroscopy of cells loaded with 2,7-bis(carboxyethyl)-5(6)-carboxyfluorescein to monitor intracellular pH (pH_i). When the volume increase achieved by these cells during Na⁺ solute absorption was duplicated by a modest 5-7% hypotonic dilution, their pH_i first acidified and then alkalinized. This alkalinization was blocked by 5-(N-methyl-N-isobutyl) amiloride (MIA; 1 µ), an inhibitor of NHE. The RVD subsequent to 5-7% hypotonic dilution was prevented by Na⁺-free medium and by amiloride and non-amiloride derivatives. The order of potency of these inhibitors was as follows: MIA > 5-(N,N-dimethyl) amiloride > cimetidine > clonidine, in keeping with the pattern attributable to NHE-1 as the isoform of NHE responsible for increase in pH_i after modest volume increases. A substantial 30% hypotonic dilution caused acidification, and RVD following this larger volume increase was not affected by MIA. To assess the effect of hypotonicity on the activity of NHE, we measured the rate of MIA-sensitive pH_i recovery from an acid load (dpH_i/dt) in 5 and 30% hypotonic media. pH_i recovery was faster in 5% hypotonic medium compared with isotonic medium and slowest in 30% hypotonic medium, which suggested that the activity of NHE was stimulated in the slightly hypotonic medium, but inhibited in the 30% hypotonic medium. To determine the role of activated NHE in RVD after a modest volume increase, cells were hypotonically diluted 7% in MIA to prevent RVD and then alkalinized by NH₄Cl or acidified by propionic acid addition. Only after alkalinization was there complete volume regulation. We conclude that in Na⁺-absorbing enterocytes, the NHE-1 isoform of Na⁺/H⁺ exchange is stimulated by volume increases that duplicate the ``physiological'' volume increase occurring when these cells absorb Na⁺-cotransported solutes. The subsequent alkalinization of pH_i is a required determinant of the osmolyte loss that underlies this distinct volume regulatory mechanism.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				S. Sanchez-Armass, S. R. Sennoune, D. Maiti, F. Ortega, and R. Martinez-Zaguilan Spectral imaging microscopy demonstrates cytoplasmic pH oscillations in glial cells Am J Physiol Cell Physiol, February 1, 2006; 290(2): C524 - C538. [Abstract] [Full Text] [PDF]

				H. L. Ebner, A. Cordas, D. E. Pafundo, P. J. Schwarzbaum, B. Pelster, and G. Krumschnabel Importance of cytoskeletal elements in volume regulatory responses of trout hepatocytes Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2005; 289(3): R877 - R890. [Abstract] [Full Text] [PDF]

				J. R. Turner and E. D. Black NHE3-dependent cytoplasmic alkalinization is triggered by Na+-glucose cotransport in intestinal epithelia Am J Physiol Cell Physiol, November 1, 2001; 281(5): C1533 - C1541. [Abstract] [Full Text] [PDF]

				J. R. Turner, E. D. Black, J. Ward, C.-M. Tse, F. A. Uchwat, H. A. Alli, M. Donowitz, J. L. Madara, and J. M. Angle Transepithelial resistance can be regulated by the intestinal brush-border Na+/H+ exchanger NHE3 Am J Physiol Cell Physiol, December 1, 2000; 279(6): C1918 - C1924. [Abstract] [Full Text] [PDF]

				D. W. Good, J. F. Di Mari, and B. A. Watts III Hyposmolality stimulates Na+/H+ exchange and HCO3- absorption in thick ascending limb via PI 3-kinase Am J Physiol Cell Physiol, November 1, 2000; 279(5): C1443 - C1454. [Abstract] [Full Text] [PDF]

				T. Sonnentag, W.-K. Siegel, O. Bachmann, H. Rossmann, A. Mack, H.-J. Wagner, M. Gregor, and U. Seidler Agonist-induced cytoplasmic volume changes in cultured rabbit parietal cells Am J Physiol Gastrointest Liver Physiol, July 1, 2000; 279(1): G40 - G48. [Abstract] [Full Text] [PDF]

				R. J. Macleod, P. Lembessis, S. James, and H. P. J. Bennett Isolation of a Member of the Neurotoxin/Cytotoxin Peptide Family from Xenopus laevis Skin Which Activates Dihydropyridine-sensitive Ca2+ Channels in Mammalian Epithelial Cells J. Biol. Chem., August 7, 1998; 273(32): 20046 - 20051. [Abstract] [Full Text] [PDF]

				F. LANG, G. L. BUSCH, M. RITTER, H. VOLKL, S. WALDEGGER, E. GULBINS, and D. HAUSSINGER Functional Significance of Cell Volume Regulatory Mechanisms Physiol Rev, January 1, 1998; 78(1): 247 - 306. [Abstract] [Full Text] [PDF]