Reversible cell injury due to compromised ionic transfer (cellular swelling): granular degeneration, vacuolar degeneration, hydropic change
Cellular injury can be reversible or irreversible. Multiple morphological changes can be shown in reversible damage:
- Cellular swelling (result of defective energy-dependent ion pumps leading to poor fluid homeostasis).
- Fatty change (increase in number of large lipid vacuoles in cytoplasm due to organelle failure)
- Plasma membrane damage (e.g. blebbing)
- Dilation of ER
- Nuclear alterations
One of the common causes of cell injury, and the precursor to many conditions, is the accumulation of abnormal amounts of substances, this can be caused by hypoxia, which causes damage to the sodium potassium membrane pump. The Sodium-potassium pump is of course an active one, thereby, what we are seeing is Hypoxia leading to disruption of the Krebs/ETC mechanism, leading to reduction in available ATP, leading to Sodium-Potassium pump disruption.
Reduction in ATP results, in fact, in four significant cellular changes:
- 1. ATP-dependent sodium pump is reduced (what this question is specifically tackling)
- 2. Increase in anaerobic glycolysis (as will be considered in question 6)
- 3. Failure of ATP-dependent Ca²⁺ pumps leading to an increase in intracellular Calcium
- 4. Prolonged depletion of ATP leads to structural disruption of ER and RER.
The failure of the Na/K pump leads to leakage of potassium into the ECM, with sodium and water moving into the cell, causing cellular swelling and increased intracellular pressure, possibly leading to membrane damage.
Macroscopically we see a change in colour to pallor, increased turgor (hydrostatic pressure), and increased weight. Microscopically we see small clear vacuoles within the cytoplasm, representing pinched-off segments of endoplasmic reticulum.
H&E, liver: severe cellular swelling of hepatocytes (ballooning, a form of hydropic degeneration) – enlarged cells with pale, clear, rarefied cytoplasm (circle), next to normal pink hepatocytes. Example from steatohepatitis.
Image: “Ballooning degeneration high mag cropped annotated” by Nephron, CC BY-SA 3.0, via Wikimedia Commons.
Example: Hydropic change is typically seen in the proximal tubular cells of the kidney and in hepatocytes after hypoxia or toxins (e.g. carbon tetrachloride). The organ is swollen, pale and heavy, and the change disappears if the cause is removed in time.
From what I can tell, the terms ‘granular degeneration, hydropic change and vacuolar degeneration’ are all synonyms for this pattern of pathological damage.