Murta J N, Serra A, Cunha-Vaz J G
Department of Ophthalmology, Hospital of University of Coimbra, Portugal.
Exp Eye Res. 1994 May;58(5):567-72. doi: 10.1006/exer.1994.1051.
Microperfusion techniques were used to characterize in vitro the fluorescein transport and fluid movement across isolated diabetic rabbit retinal vessels. Unbranched segments of arterioles of alloxan-induced diabetic rabbits were isolated and cannulated on a microperfusion apparatus. Movement of 3H-inulin, the reference tracer, and 14C-fluorescein, the test tracer, across the vascular walls was studied using microperfusion techniques adapted by us to study vascular permeability. The diabetic retinal vessels showed a fluid flux from bath to lumen of 3.6 +/- 0.6 nl min-1 mm-1 with perfusion rates of 7.1 +/- 0.3 nl min-1. This value was 43% (P < or = 0.05) lower when compared with normal values obtained in previous work. Bath to lumen fluorescein fluxes were 2.1 +/- 0.5 and 7.6 +/- 1.6 x 10(-12) mol min-1 mm-1, for fluorescein concentrations of 0.87 x 10(-4) and 1.5 x 10(-4) M, respectively. These values are 23% (P < or = 0.05) and 38.7% (P < or = 0.05), respectively, lower when compared to values obtained from normal retinal vessels. Probenecid, a competitive inhibitor of organic anion transport, added to the bath, had no effect. Increasing bath concentrations of fluorescein caused increasing fluid flux from bath to lumen, and again, probenecid added to the bath has no effect. These results show a significant decrease of fluorescein transport and of net fluid flux across diabetic retinal vessel walls from outside into the lumen, suggesting that in experimental alloxan-induced diabetes there is an early, probably functional, involvement of the retinal vessels in the initial alteration of the blood-retinal barrier (BRB).
采用微灌注技术在体外对荧光素跨孤立的糖尿病兔视网膜血管的转运及液体流动进行了表征。分离用四氧嘧啶诱导的糖尿病兔的小动脉无分支节段，并将其插管到微灌注装置上。使用我们改进的用于研究血管通透性的微灌注技术，研究了作为参考示踪剂的³H-菊粉和作为测试示踪剂的¹⁴C-荧光素跨血管壁的运动。糖尿病视网膜血管在灌注速率为7.1±0.3 nl min⁻¹时，显示出从浴槽到管腔的液体通量为3.6±0.6 nl min⁻¹ mm⁻¹。与先前工作中获得的正常值相比，该值低43%（P≤0.05）。对于荧光素浓度分别为0.87×10⁻⁴和1.5×10⁻⁴ M的情况，从浴槽到管腔的荧光素通量分别为2.1±0.5和7.6±1.6×10⁻¹² mol min⁻¹ mm⁻¹。与从正常视网膜血管获得的值相比，这些值分别低23%（P≤0.05）和38.7%（P≤0.05）。添加到浴槽中的有机阴离子转运竞争性抑制剂丙磺舒没有作用。增加浴槽中荧光素的浓度会导致从浴槽到管腔的液体通量增加，并且同样，添加到浴槽中的丙磺舒没有作用。这些结果表明，荧光素跨糖尿病视网膜血管壁从外部到管腔的转运及净液体通量显著降低，提示在实验性四氧嘧啶诱导的糖尿病中，视网膜血管在血视网膜屏障（BRB）的初始改变中存在早期的、可能是功能性的参与。
