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A journey inside the kidney: What makes proximal tubule cells so unique?
The kidneys are one of the important organs in the human body, and their functions are not limited to filtering blood and expelling waste. As a key part of the nephron, the proximal tubule plays an indispensable role. Our kidneys possess complex structure and function, especially the proximal tubule cells, which are known for their unique characteristics and roles.
Structural characteristics of proximal tubule
The proximal tubule starts from the renal pole of the renal tubule capsule and extends to the origin of the loop of Henle. At this location, capsule endothelial cells transform into proximal tubule epithelial cells. The proximal tubules can be further divided into proximal convoluted tubules and proximal straight tubules.
The most striking feature of the proximal tubule is the brush-like edge of its lining. The luminal surface of the cell is covered with dense microvilli. These microvilli significantly increase the luminal area of the cell and contribute to its reabsorption function. accomplish.
These microvilli are composed of neatly arranged actin fibers and can be visualized by fluorescence microscopy. The cytoplasm of epithelial cells contains large numbers of mitochondria, mainly concentrated in the basement membrane folds at the base of the cells, a feature that gives these cells an acidophilic appearance.
Function of the proximal tubule
In addition to their structure, the function of proximal tubule cells is also extremely important. They play a key role in the pH regulation of the filtrate by secreting hydrogen ions into the lumen and reabsorbing approximately 80% of the filtered bicarbonate.
In fluid entering the proximal convoluted tubule, sodium transport facilitates fluid reabsorption, which is driven by the sodium-potassium ATPase in the basement membrane of epithelial cells.
Sodium reabsorption in these cells relies primarily on P-type ATPase, with approximately 60-70% of the filtered sodium load being reabsorbed in the proximal tubule via active transport, solvent drag, and transcellular electrolytic diffusion. Active transport is mainly carried out through the sodium/hydrogen antiporter protein (NHE3), further improving the efficiency of reabsorption.
Clinical significance
The role of proximal tubule epithelial cells in renal pathology cannot be ignored. Most types of renal cell carcinoma, which is the most common type of kidney cancer, originate in the convoluted tubules. Acute tubular necrosis occurs when proximal tubule cells are directly damaged by toxins.
For example, antibiotics (such as constant antibiotics, myeloperoxide) and dehydration poisoning can damage proximal tubule cells.
In addition, dysfunction of the proximal tubules may lead to renal tubular acidosis (proximal type), known as Fanning syndrome, resulting in increased losses of bicarbonate, glucose, amino acids, and phosphates in the tubular filtrate.
Conclusion
These unique cell types play multiple roles in maintaining kidney health, and their role in disease processes has attracted increasing attention. The mystery of the kidney lies not only in its complex structure, but also in how these cells work together to maintain a stable internal environment in the body. Can we fully understand the function of these tubule cells and pave the way for future research?
