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19 F NMR studies of changes in membrane potential and intracellular volume during dexamethasone‐induced apoptosis in human leukemic cell lines
Author(s) -
Adebodun Foluso,
Post Jan F. M.
Publication year - 1993
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041540123
Subject(s) - intracellular , dexamethasone , extracellular , apoptosis , cell culture , chemistry , programmed cell death , cell , membrane potential , incubation , microbiology and biotechnology , biology , biochemistry , endocrinology , genetics
Abstract The induction of apoptosis in leukemic cells by dexamethasone is well known, but the mechanism of this type of cell death and of dexamethasone resistance by some variants is still poorly understood. Apoptotic cell death is preceded by many changes in cellular properties, such as glucose metabolism, cell size, cell density, and others. In this study, 19 F‐NMR has been used to characterize changes in cell membrane potential and intracellular accessible volume during dexamethasone induced apoptosis. One dex‐sensitive (CEM‐C7) and three dex‐resistant variants (CEM‐C1, CEM‐ICR27, and CEM‐4R4) were examined. We have observed separate intracellular and extracellular resonances for trifluoroacetate and trifluoroacetamide added to suspended leukemic cells. From the equilibrium distribution of these fluoro‐compounds between intra and extracellular spaces, the changes in membrane potential and intracellular accessible volume were calculated. The membrane potential for CEM‐C7 cells was found to significantly decrease in the presence of dexamethasone (9‐mV decrease within 18 h of dexamethasone treatment), while that of CEM‐ICR27 was found in some samples to increase on dexamethasone incubation. The membrane potential for CEM‐C1 decreased slightly, while that of CEM‐4R4 was not appreciably affected by dexamethasone. The reduction of membrane potential seems to be an early step in the mechanism of dexamethasone induced apoptosis. Although the intracellular volume varied with cell type and dexamethasone incubation (for CEM‐C7), the fractional intracellular volume (α = V in /V cell was found to be the same (0.82 ± 0.06) for all the cell lines in the presence and absence of dexamethasone. © 1993 Wiley‐Liss, Inc.