Theoretical and experimental discrimination between cl-/h+
symporters and cl-/oh- antiporters.
Alvarado, Francisco, and Monique Vasseur.
Institut National de la Sant[acute]e et de la Recherche
M[acute]edicale, CJF 94-07, Facult[acute]e de Pharmacie,
Universit[acute]e de Paris XI, 92296 Chatenay-Malabry, France
APStracts 3:0174C, 1996.
A Cl-/H+ symport and a Cl-/OH- antiport cannot be readily
distinguished physicochemically, but a kinetic distinction is
theoretically possible because a Cl-/H+ symporter involves a two-site
carrier whereas a Cl-/OH- antiporter involves a single-site carrier.
Accordingly, we have developed kinetic models and equations that we
have tested by studying Cl- uptake by isolated guinea-pig ileal
brush-border membrane vesicles as a function of either [Cl-] or [H+].
We conclude that a two-site Cl-/H+ symporter with a 1/1 stoichiometry
explains both the pH-dependent Cl- uptake and Cl-/Cl- exchange
activities of the brush border membrane in terms of a single, random,
non-obligatory mobile carrier where exchange occurs by counterflow.
This symport, probably involving an AE2 protein, differs therefore
functionally from the erythrocyte's band-3 anion exchanger (AE1)
which involves an antiport. The question is whether members of the AE
gene family can be functionally diverse even when their primary
structures exhibit up to 50% overall homologies.
Received 27 October 1995; accepted in final form 14 May 1996.
APS Manuscript Number C653-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96