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Titolo:
CONTROL OF H-HCO3- PLASMA-MEMBRANE TRANSPORTERS BY UREA HYPEROSMOLALITY IN RAT MEDULLARY THICK ASCENDING LIMB()
Autore:
LEVIEL F; FROISSART M; SOUALMIA H; POGGIOLI J; PAILLARD M; BICHARA M;
Indirizzi:
HOP BROUSSAIS,DEPT PHYSIOL,96 RUE DIDOT F-75674 PARIS 14 FRANCE HOP BROUSSAIS,DEPT PHYSIOL F-75674 PARIS 14 FRANCE UNIV PARIS 06,DEPT PHYSIOL,INSERM,U356 F-75674 PARIS FRANCE
Titolo Testata:
The American journal of physiology
fascicolo: 5, volume: 266, anno: 1994,
parte:, 1
pagine: 30001157 - 30001164
SICI:
0002-9513(1994)266:5<30001157:COHPTB>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
CELL-VOLUME REGULATION; NA+-H+ ANTIPORTER; BICARBONATE ABSORPTION; URINARY ACIDIFICATION; INTRACELLULAR PH; VASOPRESSIN; OSMOLALITY; ADH; HORMONE; KIDNEY;
Keywords:
INTRACELLULAR PH; INTRACELLULAR CALCIUM; SODIUM-HYDROGEN ANTIPORT; PLASMA MEMBRANE HYDROGEN-ADENOSINE-TRIPHOSPHATASE; POTASSIUM-BICARBONATE COTRANSPORT; ARGININE VASOPRESSIN; ANGIOTENSIN II; AMILORIDE; FUROSEMIDE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
21
Recensione:
Indirizzi per estratti:
Citazione:
F. Leviel et al., "CONTROL OF H-HCO3- PLASMA-MEMBRANE TRANSPORTERS BY UREA HYPEROSMOLALITY IN RAT MEDULLARY THICK ASCENDING LIMB()", The American journal of physiology, 266(5), 1994, pp. 30001157-30001164

Abstract

Hyperosmolality inhibits bicarbonate absorption by the rat medullary thick ascending limb (MTAL) by unknown mechanisms. Intracellular pH (pH(i)) was monitored with use of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein in rat MTAL tubule suspensions to specify the H+-HCO3- membrane transporters affected by hyperosmolality. Measurements were made after greater than or equal to 15-min incubation of the cells in media rendered hypertonic by urea to avoid any change in cell volume. Na+-Hantiport activity, estimated from the Na+-induced initial rate of pH(i) recovery of Na+-depleted acidified cells in the presence of 0.1 mM furosemide to inhibit Na+-K+-2Cl(-) cotransport, was inhibited by 300 mM urea and 10(-8) M arginine vasopressin (AVP) in an additive manner. Na+-H+ antiport inhibition by urea hyperosmolality was maximal at 300mM urea with a half-maximal inhibitory concentration of 75 mM and wasdue to a 28% decrease in maximum velocity (V-max) with no effect on the Michaelis constant for sodium. Urea hyperosmolality (300 mM) did not affect steady-state intracellular calcium concentration ([Ca2+](i)),assessed with use of fura 2 fluorescence, and still inhibited Na+-H+ antiport in MTAL cells loaded with ,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid to minimize any transient change in [Ca2+](i) during the preincubation in urea medium. Furthermore, 300 mM urea did notstimulate basal or AVP-induced adenosine 3',5'-cyclic monophosphate (cAMP) accumulation. Plasma membrane H+-adenosinetriphosphatase (ATPase) activity and HCO, transport, assessed by appropriate experimental protocols, were unaltered by 300 mM urea. We conclude that urea hyperosmolality directly inhibits Na+-H+ antiport, but not H+-ATPase and K+-HCO3-, cotransport, of rat MTAL cells by affecting the V-max of the antiporter independently of change in cell volume, cytosolic calcium, or cAMP.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 05/06/20 alle ore 11:44:15