Azide- and Vanadate-Sensitive M-Phase Alkalinity and Cytosolic Acidification of Chang Liver Cells

• Published in: Japanese Journal of Pharmacology 1994, Vol.65(1), pp.83-87
• Main Authors: Sit, Kwok-Hung, Paramanantham, Ramanujam, Bay, Boon-Huat, Wong, Kim-Ping
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - antagonists & inhibitors; ATPase sensitivity (F-ATPase and P-ATPase); Azides - pharmacology; Biological and medical sciences; Cell cycle, cell proliferation; Cell physiology; Cells, Cultured; Cytosol - drug effects; Cytosol - enzymology; Cytosol - metabolism; Flow cytometric evaluation (BCECF ratio); Flow Cytometry; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Liver - cytology; Liver - enzymology; Liver - metabolism; Mitosis - physiology; Molecular and cellular biology; Proton pumping (M-phase and interphase); Vanadates - pharmacology
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1254/jjp.65.83

Flow cytometric cell-by-cell evaluation of NH4Cl acidification of human Chang cells showed that at steady state, 3% of the cells remained alkalinized (>pHi 7) over an extended period (up to 80 min) despite the absence of extracellular Na+ and HCO3-. In fluorescence microscopy, the acidification-resistant cells were characteristically rounded M-phase cells. Both mean cytosolic pH and M-phase alkalinity were however sensitive to (a) azide and oligomycin, inhibitors of F-ATPase (ATP synthase), and to (b) vanadium ions, the phosphate analogue of P-ATPase (ATP-hydrolyzing), in dose-dependent and time-dependent man ners. Dead cell indices were constant at ≈ 10%. Thiocyanate chaotrophic anions, which cleave the V-ATPase structure, had no effect. Since ATP synthesizing F-ATPase (ATP synthase) is coupled to ATP-hydrolyzing P-ATPase as ''master-&-slave'', azide- and oligomycin-sensitivity corroborated with vanadate-sensitivity in suggesting energized proton pumping modulating (a) M-phase alkalinity and (b) cytosolic pH, against acidification.