Megamitochondria in hepatic and renal disease

This study was undertaken to determine the incidence and significance of enlarged mitochondria ("swollen" or "giant") in individuals with various forms of liver disease and in patients with idiopathic nephrotic syndrome. Enlarged mitochondria were observed in 20/30 liver biopsies and in 24/45 renal biopsies. They were present in hepatocytes but not in the bile duct epithelial cells and in the epithelial cells of both proximal and distal convoluted tubules of the nephron. The available experimental data indicate that enlargement of this organelle is associated with inhibition of mitochondrial respiration and uncoupling of oxidative phosphorylation. Mitochondrial swelling follows almost universally every type of cell injury but megamitochondria with intramatrical crystals appear only under certain conditions. No explanation is available for their common presence in various forms of human disease.