ISSN:
1432-1424
Keywords:
MDCK-F cells
;
Ca2+ entry
;
pH
;
Video imaging
;
Oscillations
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract We investigated the relationship between intracellular Ca2+ and pH homeostasis in Madin-Darby canine kidney-focus (MDCK-F) cells, a cell line exhibiting spontaneous oscillations of intracellular Ca2+ concentration (Ca i 2+ ). Ca i 2+ and intracellular pH (pH i ) were measured with the fluorescent dyes Fura-2 and BCECF by means of video imaging techniques. Ca2+ influx from the extracellular space into the cell was determined with the Mn2+ quenching technique. Cells were superfused with HEPES-buffered solutions. Under control conditions (pH 7.2), spontaneous Ca i 2+ oscillations were observed in virtually all cells investigated. Successive alkalinization and acidification of the cytoplasm induced by an ammonia ion prepulse had no apparent effect on Ca i 2+ oscillations. On the contrary, changes of extracellular pH value strongly affected Ca i 2+ oscillations. Extracellular alkalinization to pH 7.6 completely suppressed oscillations, whereas extracellular acidification to pH 6.8 decreased their frequency by 40%. Under the same conditions, the respective pH i changes were less than 0. 1 pH units. However, experiments with the Mn2+ quenching technique revealed that extracellular alkalinization significantly reduced Ca2+ entry from the extracellular space. Large increases of Ca i 2+ triggered by the blocker of the cytoplasmic Ca2+-ATPase, thapsigargin, had no effect on pH i We conclude: intracellular Ca2+ homeostasis in MDCK-F cells is pH dependent. pH controls Ca2+ homeostasis mainly by effects on the level of Ca2+ entry across the plasma membrane. On the contrary, the intracellular pH value seems to be insensitive to rapid changes of Ca i 2+ . The project was supported by the Deutsche Forschungsgemeinschaft, SFB-176 (A6) and by the Jubilämusstiftung of the University of Würzburg.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00232642
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