Abstract
We evaluated the role of extracellular UTP and other nucleotides in the regulation of chloride (JCl) and fluid secretion (JCl) across the pigmented rabbit conjunctiva. Jv was determined in freshly excised conjunctival tissues mounted between two buffer reservoirs maintained in an enclosed environment at 37°C. Short circuit current (Isc) and 36Cl flux were measured using modified Ussing-type chambers. Fluid flux measurements were made with a pair of capacitance probes. After observing the baseline for 15 to 30 min, fluid flux was measured in the presence of mucosally applied nucleotides (10 μM) for a period of 30 min. Mucosal application of 10 μM each of UTP, UDP, ATP, ADP, AMP, adenosine, and ATP-γ-S transiently stimulated fluid secretion across the conjunctiva to a significant extent for 10 to 15 min. Other nucleotides did not show any significant effect. The stimulation of fluid secretion correlated well with the stimulation in Isc (r2 = 0.85). UTP (0.1–1000 μM) led to a maximal increase in fluid secretion by 11.72 ± 0.48 μl/(h · cm2) with an EC50 value of 10.39 ± 1.08 μM. ATP (0.1–1000 μM) caused a maximal increase in fluid secretion by 11.89 ± 0.88 μl/(h · cm2) with an EC50 value of 17.23 ± 2.63 μM. Adenovirus type 5 (Ad5) infection significantly decreased both net 36Cl secretion across the conjunctiva by ∼56% and the rate of fluid secretion by ∼56%. UTP (10 μM), but not 1 mM 8-bromo-cAMP, was able to elicit a normal stimulatory response in the Ad5-infected tissues. In conclusion, mucosal application of purinergic nucleotides may be therapeutically important in restoring ion and fluid secretion in the diseased conjunctiva.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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DOI: 10.1124/jpet.103.049221.
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This work was supported by the National Institutes of Health Grants EY12356 (to V.H.L.L.), EY12689 (to M.D.T.), EY03040 (to M.D.T. and R.W.R.), HL38658 (to K.-J.K.), and HL64365 (to K.-J.K. and V.H.L.L.); Grant-in-Aid AHA-GIA-990542N (to K.-J.K.), Research to Prevent Blindness, Inc. (to M.D.T. and R.W.R.), American Ophthalmological Society-Herman Knapp Testimonial Fund Fellowship (1999–2000) (to R.W.R.), American Foundation for Pharmaceutical Education (to H.J.G.), and the Charles and Charlotte Krown Fellowship (to M.H.I.S.).
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ABBREVIATIONS: s-to-m, serosal-to-mucosal; Jv, rate of fluid secretion; INS365, P1,P4-di(uridine 5′-)tetraphosphate, tetrasodium salt; Isc, short circuit current; 8-Br-cAMP, 8-bromoadenosine-3′,5′-cyclic monophosphate; Ad5, adenovirus type 5; BRS, bicarbonated Ringer's solution; Jv,max, maximal rate of fluid secretion; PD, potential difference; AQP, aquaporin; TEER, trans-epithelial electrical resistance.
- Received January 15, 2003.
- Accepted March 10, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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