Murta J N, Cunha-Vaz J G, Sabo C A, Jones C W, Laski M E
Department of Ophthalmology, University of Coimbra, Portugal.
Invest Ophthalmol Vis Sci. 1990 Mar 1;31(3):471-80.
We developed an experimental model to study the permeability of individual retinal vessels in vitro using microperfusion techniques adapted from kidney tubule studies. The retinal vessels were isolated by freehand dissection and mounted on a microperfusion apparatus. When inulin was perfused luminally, it was diluted to 80.2 +/- 2.3% of its initial concentration. However, no radioactive leak into the bath side was observed, suggesting that the dilution was due to fluid flux from bath to lumen. The dilution of fluorescein (81.9 +/- 3.8%) was in the same range as that of inulin, the reference marker. The extremely low lumen-to-bath fluorescein flux, 0.5 +/- 0.9 X 10(-12) mol/min/mm, increased by 68% when probenecid was added to the perfusate and by 210% when probenecid was placed in the bath. The effect was concentration-dependent. When placed in the bath, fluorescein moved rapidly across the retinal vessel walls, accumulating in the lumen to concentrations 40 times higher than in the bath. This movement from bath to lumen, which was much higher (13.6 +/- 0.3 X 10(-12) mol/min/mm) than the lumen-to-bath fluorescein flux for the same fluorescein concentration, decreased by adding probenecid to the bath. The kinetics of this unidirectional movement of fluorescein were consistent with a saturable active transport process. The fluid flux from bath to lumen across the retinal vessels, which was 6.3 +/- 1.0 nl/min/mm for perfusion rates of 6.6 +/- 0.2 nl/min, was temperature-dependent and was coupled to the fluorescein transport. Fluorescein stimulated the fluid flux by 17% when added to the perfusate and by 60% when added to the bath, and this effect could be reversed by probenecid. Our results showed an active transport of fluorescein in the rabbit retinal vessels coupled with net fluid flux from outside the vessels into the lumen.
我们开发了一种实验模型，利用从肾小管研究中改编而来的微灌注技术，在体外研究单个视网膜血管的通透性。通过徒手解剖分离视网膜血管，并将其安装在微灌注装置上。当向管腔内灌注菊粉时，其浓度被稀释至初始浓度的80.2±2.3%。然而，未观察到放射性物质泄漏到浴液侧，这表明稀释是由于液体从浴液流向管腔。荧光素的稀释率（81.9±3.8%）与参考标志物菊粉的稀释率在同一范围内。极低的管腔到浴液的荧光素通量为0.5±0.9×10⁻¹²摩尔/分钟/毫米，当向灌注液中加入丙磺舒时增加了68%，当将丙磺舒置于浴液中时增加了210%。这种效应呈浓度依赖性。当置于浴液中时，荧光素迅速穿过视网膜血管壁，在管腔内积累，其浓度比浴液中高40倍。这种从浴液到管腔的移动（13.6±0.3×10⁻¹²摩尔/分钟/毫米）比相同荧光素浓度下管腔到浴液的荧光素通量高得多，通过向浴液中加入丙磺舒，这种移动减少。荧光素这种单向移动的动力学与可饱和的主动转运过程一致。对于6.6±0.2纳升/分钟的灌注速率，穿过视网膜血管从浴液到管腔的液体通量为6.3±1.0纳升/分钟/毫米，该通量依赖于温度，并与荧光素转运相关联。当向灌注液中加入荧光素时，其刺激液体通量增加了17%，当加入到浴液中时增加了60%，并且这种效应可被丙磺舒逆转。我们的结果表明，兔视网膜血管中存在荧光素的主动转运，并伴有从血管外到管腔的净液体通量。
