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Titolo:
INTERACTIONS OF EXTERNAL AND INTERNAL K-HCO3- COTRANSPORTER OF RAT MEDULLARY THICK ASCENDING LIMB( WITH K+)
Autore:
BLANCHARD A; LEVIEL F; BICHARA M; PODEVIN RA; PAILLARD M;
Indirizzi:
INST BIOMED CORDELIERS,INSERM U356,15 RUE ECOLE MED F-75270 PARIS 06 FRANCE UNIV PARIS 06,DEPT PHYSIOL,INSERM U356 F-75270 PARIS 06 FRANCE HOP BROUSSAIS F-75270 PARIS 06 FRANCE
Titolo Testata:
American journal of physiology. Cell physiology
fascicolo: 1, volume: 40, anno: 1996,
pagine: 218 - 225
SICI:
0363-6143(1996)40:1<218:IOEAIK>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
NA+-H+ ANTIPORTER; BICARBONATE ABSORPTION; HENLE LOOP; KIDNEY; POTASSIUM; TRANSPORT; ATPASE; CELLS; HYPEROSMOLALITY; INHIBITION;
Keywords:
BICARBONATE TRANSPORT; RENAL TUBULE; ACID-BASE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
26
Recensione:
Indirizzi per estratti:
Citazione:
A. Blanchard et al., "INTERACTIONS OF EXTERNAL AND INTERNAL K-HCO3- COTRANSPORTER OF RAT MEDULLARY THICK ASCENDING LIMB( WITH K+)", American journal of physiology. Cell physiology, 40(1), 1996, pp. 218-225

Abstract

We studied [K+](i) and [K+](o), where subscripts i and o refer to intracellular and extracellular, respectively, concentration dependency of the kinetic properties of the electroneutral K+-HCO3-, cotransport, using suspensions of rat medullary thick ascending limb (mTAL). With the use of nigericin and monensin, [K+](i) was clamped at various values, While maintaining [Na+](i) = [Na+](o) = 37 mM, [HCO3-](i) = [HCO3-](o) = 23 mM, and pH(i) = pH(o) = 7.4. As indicated by 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein HCO3--dependent rates of change in pH(i), at constant [K+](i), increasing the magnitude of the outward K+ gradient by varying [K+], saturated HCO3- efflux with a Michaelis-Mentencurve (apparent Michaelis constant for [K+](o) = 2 mM, Hill coefficient = 1). On the other hand, increasing [K+](i) from 30 to 140 mM, while either [K+](o) or the magnitude of the K+ concentration gradient wasfixed, saturated HCO3- efflux with a sigmoidal curve and yielded a Hill coefficient of 3.4 and 50% of maximum velocity at 70 mM [K+](i). These results indicate that [K+](i), independent of its role as a transportable substrate for the cotransport with HCO3-, has a role as an allosteric activator of the K+-HCO3- cotransporter. Such an allosteric modulation may contribute to the maintenance of net HCO3- absorption despite large in vivo physiological variations of K+ concentration in themedullary interstitium.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/07/20 alle ore 22:23:30