Journal
AMERICAN JOURNAL OF PHYSIOLOGY-RENAL PHYSIOLOGY
Volume 291, Issue 2, Pages F332-F340Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajprenal.00340.2005
Keywords
cell swelling; cell stretch; urothelium; cell damage
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Funding
- NIDDK NIH HHS [DK-51382] Funding Source: Medline
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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(.)min(-1.)cm(-2) (n = 18). Serosal ATP content increased as a saturating exponential function, suggesting 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(.)min(-1.)cm(-2) with a K-m of 0.49 mu M. The time course of serosal ATP release was modeled as a constant rate of release (d: mol(.)min(-1.)cm(-2)) and rate constant of hydrolysis (k(h):min(-)). In control conditions d was 18 fmol(.)min(-1)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).
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