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Urothelial function reconsidered: a role in urinary protein secretion.
1The Ronald Perelman Department of Dermatology, Kaplan Comprehensive Cancer Center, New York University Medical School, New York, NY 10016, USA.
Summary
The mammalian bladder urothelium is not just a barrier but also secretes key proteins like tissue-type plasminogen activator and urokinase into urine. This secretion is regulated and important for urinary tract function.
Area of Science:
- Urology
- Cell Biology
- Biochemistry
Background:
- Mammalian bladder epithelium is known for its role as a permeability barrier.
- The potential secretory function of urothelium in modifying urinary protein composition is less understood.
Purpose of the Study:
- To investigate the secretory capacity of mammalian urothelium.
- To identify proteins synthesized and secreted by the urothelium.
- To elucidate the regulatory mechanisms of urothelial secretion.
Main Methods:
- Analysis of protein synthesis and secretion in normal bovine urothelium.
- Investigation of cAMP- and calcium-regulated pathways.
- Comparison of urothelial and kidney-derived urinary proteins.
Main Results:
- Normal bovine urothelium synthesizes and secretes proteases (tissue-type plasminogen activator, urokinase) and a protease inhibitor (PP5).
- Secretion is polarized into the urine.
- The pathway is regulated by cAMP and calcium.
Conclusions:
- Mammalian urothelium functions as a secretory tissue, directly modifying urinary protein composition.
- Urinary plasminogen activators in ruminants are urothelium-derived, unlike in some other species.
- Urothelial secretion of proteins plays physiological or pathological roles in the urinary tract.