Acute tubular necrosis, oliguric phase
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The cells of the brush border in the proximal convoluted tubule are highly specialized, and have enormous resorptive capacity. When exposed to decreased oxygen tension (hypoxia), they rapidly become necrotic. The only cells in the body that are more sensitive to hypoxia are the cortical neurons of the central nervous system. In this photomicrograph, note that the cells in the proximal tubules are destroyed (arrow), whereas the low cuboidal epithelial cells of distal tubules are preserved. When the proximal tubular cells are destroyed, the kidney shuts down, producing little urine, the so-called "oliguric" (little urine) phase of acute renal failure due to acute tubular necrosis. If the extracellular matrix (i.e., the basement membrane) of the tubule remains intact, the epithelial cells can regenerate.