Study of fluid dynamics in the vitreous in normal and pathological eges

众所周知，玻璃体中的流体动力学取决于视网膜色素上皮（retinal pigment epithelium，RPE）的功能。我们已经报道了使用Ussing室的离体兔RPE-脉络膜的荧光素运动模式的特征，并且该系统适合于研究RPE的功能，即，主动转运功能和对外源物质扩散的屏障功能。本实验研究了羧基荧光素在离体兔视网膜色素上皮-脉络膜中的运动模式。羧基荧光素在研究细胞层屏障功能中是一种较好的示踪剂，通过计算RPE对羧基荧光素的渗透系数，可以间接推测液体穿过RPE的运动。（向内运动）被发现是通过被动扩散，而其从玻璃体到脉络膜侧的运动（向外运动）部分是通过主动运输。在30 μ M的浓度下，离体兔RPE脉络膜对羧基荧光素的向外渗透性约为向内渗透性的两倍。丙磺舒、哇巴因、2，4-二硝基苯酚和马尿酸盐显著降低了羧基荧光素的向外渗透性。饱和动力学研究表明，羧基荧光素对载体的亲和力和最大反应速度低于荧光素。BSS + GSSG组对羧基荧光素的内通透性明显低于BSS组和Krebs 'Ringer液组，提示GSSG对RPE屏障功能有一定的促进作用，羧基荧光素和Ussing's小室的使用可作为研究液体通过RPE的主动转运功能和RPE屏障功能的有效工具。

It is well known that fluid dynamics in the vitreous depends on the function of retinal pigment epithelium (RPE). We already reported characteristics of mode of fluorescein movement across the isolated rabbit RPE-choroid using Ussing's chamber and that this system is suited for studying the functions of RPE, i.e., active transporting function and barrier function against diffusion of exogenous substances. This time, we studied characteristics of mode of carboxyfluorescein movement across the isolated rabbit RPE-choroid. Carboxyfluorescein is known to be a much better tracer dye in studying the barrier function of cell layrs and it is expected that fluid movement across the RPE can be indirectly guessed by calculating the permeability coefficient of RPE to carboxyfluorescein.Movement of carboxyfluorescein across the isolated RPE-choroid from the choroid to the vitreous side (Inward movement) was found to be by passive diffusion, while its movement from the vitreous to the choroid side (Outward movement) was partly by active transport. At concentration of 30 muM, outward permeability of the isolated rabbit RPE-choroid to carboxyfluorescein was about twice of the inward permeability. Probenecid, ouabain, 2,4-dinitrophenol and hippurate significantly reduced the outward permeability to carboxyfluorescein. A saturation kinetic study revealed that affinity and maximum velocity of reaction of carboxyfluorescein to the carrier is lower than that of fluorescein. The inward permeability to carboxyfluorescein was significantly lower in BSS+GSSG than in BSS or Krebs' Ringer solution, which suggested that GSSG, oxidized glutathione, has beneficial effects on the barrier function of the RPE.The usage of carboxyfluorescein and Ussing's chamber is suggested to be a useful tool for studying active transport function which is associated with fluid movement across the RPE and barrier function of the RPE.