P2Y(2) receptor elicits PAS-positive glycoprotein secretion from rabbit conjunctival goblet cells in vivo

We investigated in vivo whether UTP and ATP increased periodic acid and Schiff's reagent (PAS)-positive glycoprotein release from rabbit conjunctival goblet cells. Fifty microL of UTP or ATP at the concentrations of 0.003, 0.03, 0.3, 3.0, 8.5% (54 microM-154 mM) or saline were applied to rabbit eyes. Impression cytology was performed on the upper nasal bulbar conjunctiva and the cells were stained with PAS. To clarify purinergic receptor-mediated involvement in this response, suramin (1%; 7 mM), P2Y(2) antagonist and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 0.01%; 167 microM), P2Y(1) antagonist were applied in the rabbit conjunctival sac for 10 min. before UTP or ATP application. Images of the specimens were taken with a digital camera mounted on a microscope and the PAS staining area was measured using an image analyzing system. UTP or ATP eye drop instillation transiently decreased the PAS staining area in a dose-dependent manner, but it gradually recovered after another 30 min. Saline instillation had no effect until 60 min. later. All of the agonists-induced declines were inhibited by pretreatment with 1% (7 mM) suramin but not 0.01% (167 microM) PPADS. UTP and ATP stimulate PAS-positive glycoprotein secretion via P2Y(2) receptor on goblet cells in the rabbit bulbar conjunctiva in vivo.