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

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted 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 Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rajendran, V. M. Articles by Binder, H. J. Search for Related Content PubMed PubMed Citation Articles by Rajendran, V. M. Articles by Binder, H. J. Social Bookmarking                      What's this?

J. Biol. Chem., Vol. 269, Issue 1, 156-160, 01, 1994

Differential modulation of Na-HCO3 cotransport and Na-H exchange by pH in basolateral membrane vesicles of rat distal colon

VM Rajendran and HJ Binder
Department of Internal Medicine, Yale University, New Haven, Connecticut 06510.

This study was designed to investigate the function of intravesicular proton on two pH gradient-dependent transport processes, a novel Na- HCO3 cotransport and a Na-H exchange, that are present in basolateral membrane vesicles of rat distal colon. Increasing intravesicular proton concentration saturated 22Na uptake via both Na-H exchange and Na-HCO3 cotransport; reduced the apparent Km for sodium for Na-H exchange from 94.9 to 35.6 mM, without alteration in the Vmax; but enhanced the Vmax for Na-HCO3 cotransport from 4.3 to 11.7 nmol/mg protein.6 s, while not changing the Km for sodium. The effect of a 10-fold proton concentration gradient at two different absolute proton concentrations on both systems was also determined. 22Na uptake via Na-HCO3 cotransport, but not via Na-H exchange, was enhanced at the higher proton concentration, indicating that the magnitude of the proton concentration gradient is primarily responsible for proton stimulation of Na-H exchange, whereas the absolute proton concentration is critical for proton enhancement of Na-HCO3 cotransport. These studies also demonstrate saturation of both transport systems as a function of intravesicular proton concentration without an exponential component. These results indicate that proton stimulated Na-H exchange and Na-HCO3 cotransport are regulated by distinct and separate mechanisms that may reflect their different cellular functions.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				M. Ikuma, J. Geibel, H. J. Binder, and V. M. Rajendran Characterization of Cl-HCO3 exchange in basolateral membrane of rat distal colon Am J Physiol Cell Physiol, October 1, 2003; 285(4): C912 - C921. [Abstract] [Full Text] [PDF]

				G I Sandle and I Butterfield Potassium secretion in rat distal colon during dietary potassium loading: role of pH regulated apical potassium channels Gut, January 1, 1999; 44(1): 40 - 46. [Abstract] [Full Text] [PDF]