Kinetics of urothelial ATP release

reports have proposed that the urothelium can sense mechanical stretch and communicate this information to sensory afferent neurons by the release of ATP into the vicinity of P2X-containing neurons. This report investigates the bidirectional release of ATP by in vitro rabbit urothelium. ATP was measured using the luciferin-luciferase assay. Immediately after washing of both sides of the epithelium, there was a linear increase in ATP content in the mucosal compart-ment with a rate of 23 6.5 fmol min1 cm2 (n 18). Serosal ATP content increased as a saturating exponential function, suggest-ing a constant rate of release and degradation of ATP by ectonucle-otidases/exonucleotidases. The presence of a serosal ectonucleotidase/ exonucleotidases was demonstrated by the time-dependent decrease in exogenously added ATP. The maximum rate of hydrolysis was 11 pmol min1 cm2 with a Km of 0.49 M. The time course of serosal ATP release was modeled as a constant rate of release (d