P2Y(2) receptor stimulation increases tear fluid secretion in rabbits.
OBJECTIVE
The purinergic P2Y(2) receptor agonists stimulate active Cl-transport across the excised rabbit conjunctival tissue in vitro. We determined whether UTP or ATP could increase the tear volume and change tear fluid composition in normal rabbits in vivo.


METHODS
Fifty mL was applied to rabbit eyes of UTP, ATP at concentrations of 0.1, 0.3, 1, 3, 8.5% (1.8-154 mM) or saline. A modified Schirmer test with topical anesthesia was performed 5, 15, 30 and 60 min after the instillation. In studies lasting 30 days, 50 microL of 0.5% UTP was applied 6 times a day for 4 weeks. Tear samples were collected from the conjunctival sac with a glass microcapillary. The protein profile of the tear fluid was analyzed by SDS-polyacrylamide gel electrophoresis and total protein was measured with the Bradford assay. The Easy-Titer rabbit IgG assay kit was used for the determination of immunoglobulin G (IgG).


RESULTS
UTP had dose-dependent stimulatory effects on tear secretion. It maximally increased tear secretion about 4-fold 15 min after its application. Similar effects were obtained with ATP. Repeated treatment with UTP reproducibly increased tear volume. Furthermore, UTP did not decrease total protein and IgG concentration in tear fluid and it had no effect on the protein profile.


CONCLUSIONS
These data indicate that activation of P2Y(2) receptor increases tear fluid secretion accompanied with some proteins in normal rabbits. The purinergic agonists, UTP and ATP, have potential therapeutic value in the treatment of dry eye.
Murakami
T
T
Ophthalmic Research Division, Santen Pharmaceutical Co., Ltd., Nara, Japan. muratada@remus.dti.ne.jp
Fujihara
T
T
Nakamura
M
M
Nakata
K
K
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000378:metabolism; D007074:Immunoglobulin G / Q000032:analysis; D007765:Lacrimal Apparatus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009883:Ophthalmic Solutions; D058910:Purinergic P2 Receptor Agonists; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058473:Receptors, Purinergic P2Y2; D013666:Tears / Q000378:metabolism*; D014544:Uridine Triphosphate / Q000494:pharmacology*
D005136:Eye Proteins; D007074:Immunoglobulin G; D009883:Ophthalmic Solutions; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; C042434:tear proteins; D000255:Adenosine Triphosphate; D014544:Uridine Triphosphate