title: Kinetics of urothelial ATP release.
abstract: Recent 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 compartment with a rate of 23 +/- 6.5 fmol x min(-1) x cm(-2) (n = 18). Serosal ATP content increased as a saturating exponential function, suggesting a constant rate of release and degradation of ATP by ectonucleotidases/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 x min(-1) x cm(-2) with a K(m) of 0.49 microM. The time course of serosal ATP release was modeled as a constant rate of release (d: mol x min(-1) x cm(-2)) and rate constant of hydrolysis (k(h): min(-)). In control conditions d was 18 fmol x min(-1) x cm(-2) and k(h) of 0.056 +/- 0.01 min(-) (n = 18). Steady-state serosal chamber content is 370 +/- 90 fmol/cm(2), and concentration is 50 +/- 1.2 x 10(-12) M. Stretching the tissue resulted in a transient fivefold increase in the rate of mucosal ATP release and a transient sixfold increase in serosal ATP release. Half-osmotic strength solutions increased mucosal release by 10-fold and serosal release by 5-fold. Tissue damage resulted in a step-increase in mucosal chamber ATP content by 6.6 +/- 1 pmol/cm(2) and serosal chamber ATP by 0.1 +/- 0.06 pmol/cm(2) (n = 5).
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston 77555-1069, USA. slewis@utmb.edu
authors.forename: Simon A
authors.initials: SA
authors.lastname: Lewis
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Lewis
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D048429:Cell Size; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism; D009092:Mucous Membrane / Q000166:cytology / Q000294:innervation / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000294:innervation / Q000378:metabolism*; D009475:Neurons, Afferent / Q000502:physiology; D009708:Nucleotidases / Q000032:analysis / Q000502:physiology; D009997:Osmotic Pressure; D011817:Rabbits; D013997:Time Factors; D019459:Urothelium / Q000166:cytology / Q000294:innervation / Q000378:metabolism*
chemical_list: D000255:Adenosine Triphosphate; D009708:Nucleotidases