Format

Send to

Choose Destination
Invest Ophthalmol Vis Sci. 2011 May 17;52(6):3254-63. doi: 10.1167/iovs.10-7042.

Identification of P2X₃ and P2X₇ purinergic receptors activated by ATP in rat lacrimal gland.

Author information

1
Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA. robin.hodges@schepens.harvard.edu

Abstract

PURPOSE:

To identify the type of purinergic receptors activated by adenosine triphosphate (ATP) in rat lacrimal gland and to determine their role in protein secretion.

METHODS:

Purinergic receptors were identified by RT-PCR, Western blot analysis, and immunofluorescence techniques. Acini from rat lacrimal gland were isolated by collagenase digestion. Acini were incubated with the fluorescence indicator fura-2 tetra-acetoxylmethyl ester, and intracellular [Ca(2+)] ([Ca(2+)](i)) was determined. Protein secretion was measured by fluorescence assay.

RESULTS:

The authors previously showed that P2X(7)receptors were functional in the lacrimal gland. In this study, they show that P2X(1-4) and P2X(6)receptors were identified in the lacrimal gland by RT-PCR, Western blot, and immunofluorescence analyses. P2X(5) receptors were not detected. ATP increased [Ca(2+)](i) and protein secretion in a concentration-dependent manner. Removal of extracellular Ca(2+) significantly reduced the ATP-stimulated increase in [Ca(2+)](i). Repeated applications of ATP caused desensitization of the [Ca(2+)](i) response. Incubation with the P2X(1) receptor inhibitor NF023 did not alter ATP-stimulated [Ca(2+)](i). Incubation with zinc, which potentiates P2X(2) and P2X(4) receptor responses, or lowering the pH to 6.8, which potentiates P2X(2) receptor responses, did not alter the ATP-stimulated [Ca(2+)](i). P2X(3) receptor inhibitors A-317491 and TNP-ATP significantly decreased ATP-stimulated [Ca(2+)](i) and protein secretion, whereas the P2X(3) receptor agonist α,β methylene ATP significantly increased them. The P2X(7) receptor inhibitor A438079 had no effect on ATP-stimulated [Ca(2+)](i) at 10(-6) M but did have an effect at 10(-4) M.

CONCLUSIONS:

Purinergic receptors P2X(1-4) and P2X(6) are present in the lacrimal gland. ATP uses P2X(3) and P2X(7) receptors to stimulate an increase in [Ca(2+)](i) and protein secretion.

PMID:
21421865
PMCID:
PMC3109027
DOI:
10.1167/iovs.10-7042
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Silverchair Information Systems Icon for PubMed Central
Loading ...
Support Center