Liu Y, Wakakura M
Department of Ophthalmology, Kitasato University School of Medicine, Sagamihara, Japan.
Jpn J Ophthalmol. 1998 Jan-Feb;42(1):33-40. doi: 10.1016/s0021-5155(97)00104-4.
Adenosine 5'-triphosphate (ATP) and its metabolic products function as neurotransmitters or neuromodulators under the control of P1/P2-purinergic receptors. To determine the presence of these receptors on retinal Müller cells, spectrofluorometry was carried out on intracellular calcium mobilization, using Fura-2 images. Müller cells were cultured from adult rabbit retinas. Cytosolic calcium ([Ca2+]i) increased dose dependently with the application of ATP. This response was not blocked when a calcium channel blocker, nifedipine, was present, but this response was blocked, for the most part, when a P2 receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) was present. Increase in [Ca2+]i was noted by the A1 or A2 agonist, which was blocked completely by each antagonist. Response to the A1 agonist was apparent only at high concentrations. Increase in [Ca2+]i was seen in some cells following administration of the P2x agonist, methylene ATP, only at a high concentration (100 microM) but not in the presence of PPADS (50 nM). The greatest increase in [Ca2+]i was induced by a P2y agonist, methyl thio ATP at 1 to 10 microM, which was completely blocked by PPADS. Cultured Müller cells are thus shown quite likely to possess the P1-/P2-purinergic receptors including A2 and P2y.
5'-三磷酸腺苷（ATP）及其代谢产物在P1/P2嘌呤能受体的控制下作为神经递质或神经调质发挥作用。为了确定视网膜穆勒细胞上这些受体的存在，使用Fura-2成像对细胞内钙动员进行了荧光分光光度法检测。穆勒细胞从成年兔视网膜中培养。随着ATP的应用，胞质钙（[Ca2+]i）呈剂量依赖性增加。当存在钙通道阻滞剂硝苯地平时，这种反应并未被阻断，但当存在P2受体拮抗剂磷酸吡哆醛-6-偶氮苯基-2',4'-二磺酸（PPADS）时，这种反应在很大程度上被阻断。A1或A2激动剂可引起[Ca2+]i增加，每种拮抗剂均可完全阻断该反应。仅在高浓度时，对A1激动剂的反应才明显。仅在高浓度（100μM）下给予P2x激动剂亚甲基ATP后，在一些细胞中可观察到[Ca2+]i增加，但在存在PPADS（50 nM）时则未观察到。1至10μM的P2y激动剂甲基硫代ATP诱导的[Ca2+]i增加最为显著，该反应被PPADS完全阻断。因此，培养的穆勒细胞很可能拥有包括A2和P2y在内的P1-/P2嘌呤能受体。
