ISSN:
1432-2013
Keywords:
Key words pHi
;
SNARF
;
Carotid body
;
Type-1 cell
;
Potassium-hydrogen exchange
;
K+-H+ exchanger (KHE)
;
Nigericin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Intracellular pH (pHi) was measured in enzymically isolated, neonatal rat carotid body type-1 cells, using the fluorophore carboxy-SNARF-1 (AM-loaded), and using the nigericin technique for in situ fluorescence calibration (nigericin is a membrane-soluble K+-H+ exchanger). In CO2/HCO3 –-free media, inhibiting Na+-H+ exchange produced a prompt fall of pHi (background acid-loading), the rate of which was reduced by raising the extracellular K+ concentration, [K+]o. pHi recovery from an intracellular acid or alkali load was also sensitive to changes of [K+]o. These results are similar to those of Wilding et al. (J Gen Physiol 100:593–608, 1992), who proposed the existence of an acid-loading, K+-H+ exchanger (KHE) in the type-1 cell. However, when nigericin was not used for post-experimental calibration, and the superfusion system was flushed exhaustively with strong detergent, alcohol and distilled water, then background acid-loading was attenuated, and the K+ o sensitivity of pHi insignificant. Background loading was increased again, and K+ o sensitivity restored, when cells were monitored in a superfusion system which had previously been exposed to a single nigericin-calibration protocol (followed by a short system wash with strong detergent and distilled water). We conclude that the previously reported expression of KHE in carotid body type-1 cells is an artefact caused by nigericin contamination. We have therefore quantified the pHi dependence of background loading in uncontaminated type-1 cells. We consider the possible implications of our work for reports of KHE in other cell types.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050417
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