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Titolo:
NH4-H+ EXCHANGERS OF THICK ASCENDING LIMBS OF RAT-KIDNEY - EVIDENCE FROM ISOLATED MEMBRANES( AS A SUBSTRATE FOR APICAL AND BASOLATERAL NA+)
Autore:
BLANCHARD A; ELADARI D; LEVIEL F; TSIMARATOS M; PAILLARD M; PODEVIN RA;
Indirizzi:
CTR RECH BIOMED CORDELIERS,INSERM,U356,15 RUE ECOLE MED F-75270 PARIS06 FRANCE CTR RECH BIOMED CORDELIERS,INSERM,U356 F-75270 PARIS 06 FRANCE UNIV PARIS 06,HOTEL DIEU,FAC MED BROUSSAIS,LAB PHYSIOL & ENDOCRINOL CELLULAIRE RENALE F-75252 PARIS 05 FRANCE
Titolo Testata:
Journal of physiology
fascicolo: 3, volume: 506, anno: 1998,
pagine: 689 - 698
SICI:
0022-3751(1998)506:3<689:NEOTAL>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
PROXIMAL TUBULE; FUNCTIONAL-PROPERTIES; NA/H EXCHANGER; TRANSPORT; EXPRESSION; ABSORPTION; MECHANISMS; VESICLES; AMMONIUM; NHE-3;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
30
Recensione:
Indirizzi per estratti:
Citazione:
A. Blanchard et al., "NH4-H+ EXCHANGERS OF THICK ASCENDING LIMBS OF RAT-KIDNEY - EVIDENCE FROM ISOLATED MEMBRANES( AS A SUBSTRATE FOR APICAL AND BASOLATERAL NA+)", Journal of physiology, 506(3), 1998, pp. 689-698

Abstract

1. We have used highly purified right-side-out luminal and basolateral membrane vesicles (LMVs and BLMVs) isolated from rat medullary thickascending limb (MTAL) to study directly the possible roles of the LMVand BLMV Na+-H+ exchangers in the transport of NH4+. 2. Extravesicular NH4+ ((NH4+)(o)) inhibited outward H+ gradient-stimulated Na-22(+) uptake in both types of vesicles. This inhibition could not be accounted for by alteration of intravesicular pH (pH(i)). 3. Conversely, in both plasma membrane preparations, the imposition of outward NH4+ gradients stimulated Na-22(+) uptake at the acidic pH(i) (6.60) of MTAL cells, under conditions in which possible alterations in pH(i) were prevented. All NH4+ gradient-stimulated Na+ uptake was sensitive to 0.5 mM 5-(N,N-dimethyl)-amiloride. 4. The BLMV and LMV Na+-H+ exchangers had asimilar apparent affinity for internal H+ (H-i(+)), with pK(-log of dissociation constant) values of 6.58 and 6.52, respectively. 5. These findings indicate that NH4+ interacts with the external and internal transport sites of the LMV and BLMV Na+-H+ antiporters, and that both of these exchangers can mediate the exchange of internal NH4+ ((NH4+)(i)) for external Na+ (Na-o(+)) at the prevailing pH(i) of MTAL cells. 6. We conclude that operation of the BLMV Na+-H+ exchanger on the NH4+-Na+ mode may represent an important pathway for mediating the final step of NH4+ absorption, whereas transport of NH4+ on the apical antiporter may provide negative feedback regulation of NH4+ absorption.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/08/20 alle ore 16:42:48