Y. Liu et M. Wakakura, P-1- P-2-PURINERGIC RECEPTORS ON CULTURED RABBIT RETINAL MULLER CELLS/, Japanese Journal of Ophthalmology, 42(1), 1998, pp. 33-40
Adenosine 5'-triphosphate (ATP) and its metabolic products function as
neurotransmitters or neuromodulators under the control of P-1/P-2-pur
inergic receptors. To determine the presence of these receptors on ret
inal Muller cells, spectrofluorometry was carried out on intracellular
calcium mobilization, using Fura-2 images. Muller cells were cultured
from adult rabbit retinas. Cytosolic calcium ([Ca2+](i)) increased do
se dependently with the application of ATP. This response was not bloc
ked when a calcium channel blocker, nifedipine, was present, but this
response was blocked, for the most part, when a P-2 receptor antagonis
t, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) was pr
esent. Increase in [Ca2+](i) was noted by the A(1) or A(2) agonist, wh
ich was blocked completely by each antagonist. Response to the A(1) ag
onist was apparent only at high concentrations. Increase in [Ca2+](i)
was seen in some cells following administration of the P-2x agonist, m
ethylene ATP, only at a high concentration (100 mu M) but not in the p
resence of PPADS (50 nM). The greatest increase in [Ca2+](i) was induc
ed by a P-2y agonist, methyl thio ATP at 1 to 10 mu M, which was compl
etely blocked by PPADS. Cultured Muller cells are thus shown quite lik
ely to possess the P-1-/P-2-purinergic receptors including A(2) and P-
2y. (C) 1998 Japanese Ophthalmological Society.