Changes in elemental concentrations are associated with early stages of apoptosis in human monocyte-macrophages exposed to oxidized low-density lipoprotein: an X-ray microanalytical study

This study examines ion homeostasis in monocyte–macrophages committed to death by apoptosis. X‐ray microanalysis has been used to demonstrate that intracellular concentrations of potassium decreased whilst those of sodium increased following 3 h of exposure to 100 µg/ml of oxidized low‐density lipoprotein (LDL) in vitro. In contrast, the maximal incidence of cell death, as determined by the inability to exclude trypan blue, was not seen until 24 h of exposure. At 12 h, less than 1 per cent of cells were stained using terminal transferase‐mediated DNA nick‐end labelling, which is generally accepted as a marker of late stages in the apoptotic pathway. This is the first demonstration of early perturbations of ion homeostasis in monocyte–macrophages exposed to concentrations of oxidized LDL known to cause apoptosis. Copyright © 1999 John Wiley & Sons, Ltd.