ISSN:
1432-1424
Schlagwort(e):
pH regulation
;
pH i maintenance
;
Na+/H+ exchange
;
Na+-dependent Cl−/HCO3 − exchange
;
Na+-independent Cl−/HCO3 − exchange
;
36Cl− Efflux
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Chemie und Pharmazie
Notizen:
Abstract pH i recovery in acid-loaded Ehrlich ascites tumor cells and pH i maintenance at steady-state were studied using the fluorescent probe BCECF. Both in nominally HCO 3 − -free media and at 25 mm HCO 3 − , the measured pH i (7.26 and 7.82, respectively) was significantly more alkaline than the pH i . value calculated assuming the transmembrane HCO 3 − gradient to be equal to the Cl− gradient. Thus, pH i in these cells is not determined by the Cl− gradient and by Cl−/HCO 3 − exchange. pH i recovery following acid loading by propionate exposure, NH 4 + withdrawal, or CO2 exposure is mediated by amiloride-sensitive Na+/H+ exchange in HCO3 − free media, and in the presence of HCO 3 − (25 mm) by DIDS-sensitive, Na+-dependent Cl−/HCO 3 − exchange. A significant residual pH i recovery in the presence of both amiloride and DIDS suggests an additional role for a primary active H+ pump in pH i regulation. pH i maintenance at steady-state involves both Na+/H+ exchange and Na+-dependent Cl−/HCO 3 − exchange. Acute removal of external Cl− induces a DIDS-sensitive, Na+-dependent alkalinization, taken to represent HCO 3 − influx in exchange for cellular Cl−. Measurements of 36Cl− efflux into Cl−-free gluconate media with and without Na+ and/or HCO 3 − (10 mm) directly demonstrate a DIDS-sensitive, Na+ dependent Cl−/HCO 3 − exchange operating at slightly acidic pH i (pHo 6.8), and a DIDS-sensitive, Na+-independent Cl−/HCO 3 − exchange operating at alkaline pH i (pH o 8.2).
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00232640
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