Two distinct HCO(-)(3)-dependent H(+) efflux pathways in human vascular endothelial cells.
Intracellular pH (pH(i)) regulation in human umbilical vein endothelial cells (HUVEC) was investigated. The pH(i) was recorded using seminaphthorhodafluor-1 (SNARF-1). Cells were intracellularly acid loaded with NH(4)Cl prepulse. In HEPES-buffered Tyrode (nominally HCO(-)(3) free), pH(i) recovery from acid load was inhibited by 1.5 mM amiloride or Na(+)-free solution. Additionally, in HCO(-)(3)-buffered Tyrode, a HCO(-)(3)-dependent pH(i) recovery from acidosis was evident in the presence of 1.5 mM amiloride, which mediated complete recovery of pH(i) (7.26). In Na(+)-free solution, the HCO(-)(3)-dependent acid extruder mediated pH(i) recovery after an acid load but only back to 7.09. These results suggest that there are two HCO(-)(3)-dependent acid extruders in the HUVEC. One is Na(+) dependent, and the other is Na(+) independent. The former was further shown to be completely inhibited by 0.5 mM DIDS, whereas the latter was only inhibited by 24.6%. In Cl(-)-free solution, both of the HCO(-)(3)-dependent pathways were inhibited. In conclusion, one HCO(-)(3)-dependent acid extruder in the HUVEC resembles the Na(+)-dependent Cl(-)/HCO(-)(3) exchange found in other tissues, and the other is Cl(-) dependent but Na(+) independent.
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University Laboratory of Physiology, Oxford OX1 3PT, United Kingdom. bings@mrl.oapi.com
Vaughan-Jones
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Kambayashi
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D001639:Bicarbonates / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007552:Isotonic Solutions / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism
D001639:Bicarbonates; D007552:Isotonic Solutions; D017923:Sodium-Hydrogen Exchangers; C037692:Tyrode's solution