Coupling between the intracellular pH and the active transport of sodium in an epithelial cell line from Xenopus laevis.
1. The relationship between the rate of active Na+ transport and intracellular pH (pHi, measured as the BCECF fluorescence) was studied in A6 monolayers in the presence of CO2. The total buffering power (beta total) and its components (beta i and beta CO2) were assessed at various pHi. 2. The activity of Na+/H+ and Cl-/HCO3- exchangers were expressed in A6 cells; both antiports were found to participate in pHi homeostasis under standard conditions. 3. Alterations in the rate of Na+ transport induced variations in pHi. 4. Na+ transport rate was a hyperbolic function of external Na+ concentration. The curve was shifted by changing pHi: a mixed inhibition of Na+ transport by pHi was found. 5. The pHi appears as a possible mediator coupling the rate of Na+ transport across the apical and the basolateral membrane in tight epithelia.
Chuard
F
F
Institute of Physiology, University of Fribourg, Switzerland.
Durand
J
J
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002021:Buffers; D002460:Cell Line; D004848:Epithelium / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D014982:Xenopus laevis
D002021:Buffers; D000584:Amiloride; D012964:Sodium