Influence of extracellular pH and perfusion rate on Na+/H+ exchange in cultured opossum kidney cells
Studies were undertaken in cultured opossum kidney (OK) cells to determine whether the rate of H+ secretion by apical membrane Na+/H+ exchange is modulated by changes in extracellular pH or perfusion rate. H+ secretion was assessed in single cells by measuring the rate of Na(+)-dependent intracellul...
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Veröffentlicht in: | Pflügers Archiv 1992-02, Vol.420 (2), p.153-158 |
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Sprache: | eng |
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Zusammenfassung: | Studies were undertaken in cultured opossum kidney (OK) cells to determine whether the rate of H+ secretion by apical membrane Na+/H+ exchange is modulated by changes in extracellular pH or perfusion rate. H+ secretion was assessed in single cells by measuring the rate of Na(+)-dependent intracellular pH recovery after NH4Cl loading, using the pH-sensitive fluorescent dye, 2'7'-bis(carboxyethyl)-5,6-carboxyfluorescein, in monolayers mounted to allow independent perfusion of the apical and basolateral surfaces. At constant intracellular pH, Na(+)-dependent H+ secretion was found to be inversely related to extracellular H+ activity, and directly related to the perfusate flow rate. Inhibition of H+ secretion by perfusate acidity occurred immediately and was greater when perfusate Na+ was reduced, consistent with H+ competition with Na+ for binding to the transporter. By contrast, the effect of the perfusion rate was a delayed response, requiring 20 min of exposure, and was independent of perfusate Na+ concentration. The results indicate that both extracellular pH and the perfusion rate modulate H+ secretion by OK cells, and that the two effects are independent. |
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ISSN: | 0031-6768 1432-2013 |
DOI: | 10.1007/BF00374984 |