Korte G E, Bellhorn R W, Burns M S
Invest Ophthalmol Vis Sci. 1983 Jul;24(7):962-71.
It has been shown previously that the blood-retinal barrier (BRB) of rats with phototoxic retinopathy is permeable to sodium fluorescein and to fluoresceinated dextrans as large as 32A ESR (Einstein-Stokes radius). The leakage presumably occurs from retinal capillaries that have invaded the retinal pigment epithelium (RPE) and become fenestrated. In this report, the ultrastructural tracers horseradish peroxidase and catalase were used to further localize the leakage site, and to evaluate the size limit of molecules penetrating the phototoxic BRB. Horseradish peroxidase (HRP: 30A ESR) freely penetrates the BRB of phototoxic rats, since it is present in the retinal extracellular space 10 min after intravenous injection. HRP penetrates the fenestrae of capillaries which invade the RPE from the retina. It then diffuses along the pericapillary space of the intraepithelial capillaries, which is confluent with that of their parent retinal capillaries, and into the retinal extracellular space. HRP thus circumvents the tight junctions between RPE cells and between capillary endothelial cells, which appear intact in thin sections. Catalase (52A ESR) does not freely penetrate the BRB of phototoxic rats. As long as 40 min after intravenous injection, catalase is still confined to the lumen of fenestrated capillaries in the RPE, retinal capillaries, and the choriocapillaris. Although present in intraendothelial vesicles, no evidence of deposition in the pericapillary space is observed. It is concluded fenestrated capillaries in the RPE are a major site where blood-borne tracers penetrate the BRB in phototoxic retinopathy.
先前已表明，患有光毒性视网膜病变的大鼠的血视网膜屏障（BRB）对荧光素钠和高达32A ESR（爱因斯坦-斯托克斯半径）的荧光标记葡聚糖具有通透性。这种渗漏可能发生在侵入视网膜色素上皮（RPE）并形成有窗孔的视网膜毛细血管处。在本报告中，使用超微结构示踪剂辣根过氧化物酶和过氧化氢酶来进一步定位渗漏部位，并评估穿透光毒性BRB的分子的大小限制。辣根过氧化物酶（HRP：30A ESR）可自由穿透光毒性大鼠的BRB，因为静脉注射后10分钟它就存在于视网膜细胞外间隙中。HRP穿透从视网膜侵入RPE的毛细血管的窗孔。然后它沿着上皮内毛细血管的周毛细血管间隙扩散，该间隙与其母视网膜毛细血管的间隙相连，并进入视网膜细胞外间隙。因此，HRP绕过了RPE细胞之间以及毛细血管内皮细胞之间的紧密连接，这些紧密连接在薄切片中看起来完好无损。过氧化氢酶（52A ESR）不能自由穿透光毒性大鼠的BRB。静脉注射后长达40分钟，过氧化氢酶仍局限于RPE、视网膜毛细血管和脉络膜毛细血管中有窗孔的毛细血管腔内。尽管存在于内皮小泡中，但未观察到在周毛细血管间隙中有沉积的证据。得出的结论是，RPE中有窗孔的毛细血管是血源示踪剂在光毒性视网膜病变中穿透BRB的主要部位。
