| Title |
Na+-H+ exchange and intracellular pH regulation in colonocytes from the chick |
| Authors |
Calonge, ML , DE LA HORRA PADILLA, CARMEN, Ilundain, AA |
| External publication |
Si |
| Means |
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES |
| Scope |
Article |
| Nature |
Científica |
| Publication date |
26/04/1997 |
| ISI |
A1997YD65600012 |
| DOI |
10.1016/S0005-2736(96)00264-7 |
| Abstract |
The involvement of Na+-H+ exchange in chicken colonocyte homeostasis was investigated. Colonocyte pH (pH(i)) was measured with 2\',7\'-bis(carboxyethyl)-5,6-carboxyfluore (BCECF). The proton ionophore FCCP reduced basal pH(i), indicating that cytosolic [H+] is not at electrochemical equilibrium across the membrane. External Na+ removal decreased pH(i) and subsequent addition of Na+ returns pH(i) towards its control value. The rate of pH(i) recovery from an acid load was Na+-dependent (K-m for Na+, 24 mM) and inhibited by EIPA (IC50, 0.18 mu M). The initial rate of Na+-dependent cell alkalization increased as the pH(i) decreased from 7.2 to 6.6 (Hill coefficient, 1.88). Radioisotope flux studies revealed that an outwardly directed proton gradient transiently stimulated Na+ uptake into BBMV isolated from the chick colon. EIPA and amiloride inhibited pH gradient-driven Na+ uptake (IC50 of 4 mu M and 32 mu M, respectively). The K-m for Na+ of pH gradient-driven Na+ uptake was 6.8 mM. The Hill coefficient of the relationship between the initial rate of pH-driven Na+ uptake and the intravesicular pH was 0.70. It is concluded that a Na+-H+ exchanger is involved in pH(i) homeostasis in chicken colonocytes and that these cells possess at least two types of Na+-H+ antiporters with different sensitivity to EIPA and different kinetic parameters. |
| Keywords |
brush border; vesicle; colon; sodium ion-proton exchanger; amiloride; 5-(N-ethyl-N-isopropyl)-amiloride |
| Universidad Loyola members |
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