Functional and molecular characterization of lumenal and
basolateral cl-/hco3- exchangers of rat thick limbs.
Eladari, Dominique, Anne Blanchard, Fran[cedilla]coise Leviel, Michel
Paillard, Alan K. Stuart-Tilley, Seth L. Alper and Ren[acute]e
-Alexandre Podevin.
laboratoire de Physiologie et Endocrinologie Cellulaire
R[acute]enale, Facult[acute]e de M[acute]edecine Broussais
-H[circumflex]otel Dieu, (Institut National de la Sant[acute]e et de
la Recherche M[acute]edicale, U356, Paris, France)1, and the
Departments of Cell Biology and Medicine, Harvard Medical School, and
the Molecular Medicine and Renal Units, Beth Israel Hospital, Boston,
Massachusetts 022152.
APStracts 5:0096F, 1998.
Cl-/HCO3- exchange was measured in lumenal (LMV) and basolateral
(BLMV) membrane vesicles purified from rat medullary thick ascending
limb (MTAL). Cl-/HCO3- exchange in BLMV and LMV was inhibited by
4,4'-diisothiocyanatostilbene-2,2'-disulfonate_(DIDS) with respective
IC50 values of 3.2 +/- 0.9 and 15.2 +/- 5.2 _M, whereas Cl-
conductances were DIDS-insensitive. At constant external pH BLMV
36Cl-/HCO3- and 36Cl-/Cl- exchanges exhibited a sigmoidal pattern of
activation as internal pH (pHi) increased from 6.1 to 8.0, whereas
LMV 36Cl-/Cl- exchange was unchanged between pHi 6.7 and 7.8. 165 kDa
AE2 polypeptide and 115 kDa AE1-related polypeptide were present only
in BLMV. In contrast, AE1-related polypeptides of 90 and 95 kDa were
present not only in BLMV, but also (in variable abundance) in LMV. We
conclude that rat MTAL BLMV and LMV express distinct anion exchange
activities and distinct sets of AE polypeptides. AE2 (and perhaps
AE1) in BLMV likely contribute to HCO3- absorption. In contrast, LMV
exchangers may contribute to NaCl absorption via parallel coupling
with the lumenal Na+/H+ antiporters, and/or may provide negative
feedback regulation of HCO3- absorption.
Received 7 January 1998; accepted in final form 7 May 1998.
APS Manuscript Number F4-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 16 June 1998