A tissue preparation is experimentally subjected to a hypoxic environment. The cells in this tissue begin to swell, and chromatin begins to clump in cell nuclei. ATPases are activated, and ATP production decreases. Which of the following ions accumulating in mitochondria and the cytosol contributes most to these findings and to eventual cell death?
Irreversible cellular injury is likely to occur when cytoplasmic calcium increases. Calcium can enter cells and also accumulate in mitochondria and endoplasmic reticulum. The excess calcium activates ATPases, phospholipases, proteases, and endonucleases, which injure cell components. Mitochondrial permeability is increased to release cytochrome c, which activates caspases leading to apoptosis. Of the other ions listed, sodium enters the cell, while potassium diffuses out when the sodium pump fails as ATP levels fall; but this is potentially reversible.
Ca2+
Cl-
HCO3-
K+
Cellular Pathology