Kinetics of urothelial ATP release

Area of Science:

• Urothelial physiology
• Cell signaling
• Biochemistry

Background:

• The urothelium is increasingly recognized for its sensory functions.
• Mechanical stretch is proposed to trigger ATP release from the urothelium.
• ATP release may signal to sensory afferent neurons via P2X receptors.

Purpose of the Study:

• To investigate the bidirectional release of ATP by in vitro rabbit urothelium.
• To quantify ATP release rates under various conditions, including mechanical stretch and osmotic changes.
• To characterize the degradation of ATP by urothelial ectonucleotidases.

Main Methods:

• ATP was measured using the luciferin-luciferase assay in mucosal and serosal compartments of in vitro rabbit urothelium.
• ATP release rates were determined under basal conditions, mechanical stretch, hypotonic stress, and following tissue damage.
• Ectonucleotidase activity was assessed by measuring the degradation of exogenously added ATP.

Main Results:

• Basal mucosal ATP release rate was 23 +/- 6.5 fmol x min(-1) x cm(-2).
• Serosal ATP release followed a saturating exponential function, indicating release and degradation.
• Mechanical stretch increased mucosal and serosal ATP release fivefold and sixfold, respectively.
• Hypotonic solutions increased mucosal and serosal ATP release tenfold and fivefold, respectively.
• Tissue damage caused a significant increase in mucosal and serosal ATP content.

Conclusions:

• The urothelium actively releases ATP bidirectionally.
• Mechanical stretch and osmotic changes significantly modulate urothelial ATP release.
• These findings support the role of urothelial ATP release in mechanotransduction and signaling to afferent neurons.