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Titolo:
EFFECT OF EXPRESSING THE WATER CHANNEL AQUAPORIN-1 ON THE CO2 PERMEABILITY OF XENOPUS OOCYTES
Autore:
NAKHOUL NL; DAVIS BA; ROMERO MF; BORON WF;
Indirizzi:
TULANE UNIV,SCH MED,DEPT MED,SL45,1430 TULANE AVE NEW ORLEANS LA 70112 YALE UNIV,SCH MED,DEPT CELLULAR & MOL PHYSIOL NEW HAVEN CT 06520
Titolo Testata:
American journal of physiology. Cell physiology
fascicolo: 2, volume: 43, anno: 1998,
pagine: 543 - 548
SICI:
0363-6143(1998)43:2<543:EOETWC>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
CELL CHIP28 PROTEIN; COLLECTING DUCT; APICAL MEMBRANE; RAT-KIDNEY; CLONING; TRANSPORT; CDNA; SELECTIVITY; PROTON; TUBULE;
Keywords:
INTRACELLULAR PH;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
N.L. Nakhoul et al., "EFFECT OF EXPRESSING THE WATER CHANNEL AQUAPORIN-1 ON THE CO2 PERMEABILITY OF XENOPUS OOCYTES", American journal of physiology. Cell physiology, 43(2), 1998, pp. 543-548

Abstract

It is generally accepted that gases such as CO2 cross cell membranes by dissolving in the membrane lipid. No role for channels or pores in gas transport has ever been demonstrated. Here we ask whether expression of the water channel aquaporin-1 (AQP1) enhances the CO2 permeability of Xenopus oocytes. We expressed AQP1 in Xenopus oocytes by injecting AQP1 cRNA, and we assessed CO2 permeability by using microelectrodes to monitor the changes in intracellular pH (pH(i)) produced by adding 1.5% CO2/10 mM HCO3- to (or removing it from) the extracellular solution. Oocytes normally have an undetectably low level of carbonic anhydrase (CA), which eliminates the CO2 hydration reaction as a rate-limiting step. We found that expressing AQP1 (vs. injecting water) had no measurable effect on the rate of CO2-induced pH(i) changes in such low-CA oocytes: adding CO2 caused pH(i) to fall at a mean initial rate of11.3 x 10(-4) pH units/s in control oocytes and 13.3 x 10(-4) pH units/s in oocytes expressing AQP1. When we injected oocytes with water, and a few days later with CA, the CO2-induced pH(i) changes in these water/CA oocytes were more than fourfold faster than in water-injected oocytes (acidification rate, 53 x 10(-4) pH units/s). Ethoxzolamide (ETX; 10 mu M), a membrane-permeant CA inhibitor, greatly slowed the pH(i) changes (16.5 x 10(-4) pH units/s). When we injected oocytes with AQP1 cRNA and then CA, the CO2-induced pH(i) changes in these AQP1/CA oocytes were similar to 40% faster than in the water/CA oocytes (75 x 10(-4) pH units/s), and ETX reduced the rates substantially (14.7 x 10(-4) pH units/s). Thus, in the presence of CA, AQP1 expression significantly increases the CO2 permeability of oocyte membranes. Possible explanations include 1) AQP1 expression alters the lipid composition of the cell membrane, 2) AQP1 expression causes overexpression of a native gas channel, and/or 3) AQP1 acts as a channel through which CO2 can permeate. Even if AQP1 should mediate a CO2 flux, it would remain to be determined whether this CO2 movement is quantitatively important.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/10/20 alle ore 01:01:56