Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark.
Invest Ophthalmol Vis Sci. 2010 Dec;51(12):6681-7. doi: 10.1167/iovs.10-5753. Epub 2010 Aug 4.
The retinal blood flow is regulated by the tone of resistance arterioles, which is influenced by purinergic compounds such as adenosine and adenosine 5'-triphosphate (ATP) released from the retinal tissue. However, it is unknown what cellular elements in the perivascular retina are responsible for the effect of purines on the tone of retinal arterioles.
Porcine retinal arterioles were loaded with the calcium-sensitive fluorophore Oregon green. The vessels were mounted in a confocal myograph for simultaneous recordings of tone and calcium activity in cells of the vascular wall during stimulation with ATP and adenosine, with and without modifiers of these compounds. Additionally, immunohistochemistry was used to localize elements with calcium activity in the vascular wall.
Hyperfluorescence indicating calcium activity was recorded in a population of abundant round boutons interspersed in a network of vimentin-positive processes located immediately external to the smooth muscle cell layer but internal to the perivascular glial cells. These structures showed calcium activity when the vessel was relaxed with ATP but not when it was relaxed with adenosine. Ryanodine reduced calcium activity in the boutons, whereas the ATP antagonist adenosine-5'-O-(α, β- methylene diphosphate) reduced calcium activity in both the boutons and vascular tone.
The vasodilating effect of purines in porcine retinal tissue involves ATP-dependent calcium activity in a layer of cellular boutons located external to the vascular smooth muscle cells and internal to the perivascular glial cells.
视网膜血流受阻力小动脉张力调节，而小动脉张力受嘌呤类化合物如腺苷和三磷酸腺苷（ATP）影响，这些物质由视网膜组织释放。然而，尚不清楚血管周围视网膜中的哪些细胞成分负责嘌呤对视网膜小动脉张力的影响。
用钙敏感荧光染料 Oregon green 负载猪视网膜小动脉。血管被安装在共聚焦肌描记器中，用于在刺激 ATP 和腺苷时同时记录血管壁细胞的张力和钙活性，同时用这些化合物的调节剂进行刺激。此外，还使用免疫组织化学来定位血管壁中具有钙活性的元素。
在平滑肌细胞层外、血管周围神经胶质细胞内的 vimentin 阳性过程网络中，记录到大量圆形小结的钙活性超荧光，这些小结呈网络状分布，在血管松弛时，这些结构在 ATP 刺激下显示钙活性，但在腺苷刺激下不显示钙活性。Ryanodine 降低小结中的钙活性，而 ATP 拮抗剂腺苷-5'-O-（α，β-亚甲基二磷酸）降低小结和血管张力中的钙活性。
嘌呤在猪视网膜组织中的血管舒张作用涉及位于血管平滑肌细胞外、血管周围神经胶质细胞内的一层细胞小结中的 ATP 依赖性钙活性。
