Bunt-Milam A H, Saari J C, Bredberg D L
Prog Clin Biol Res. 1985;190:151-70.
The interstitial space has been characterized using immunocytochemical and biochemical techniques. The pore size of the external limiting membrane that forms the vitread margin of this extracellular space has been probed using a series of biotinylated proteins of known Stokes' radius, followed by avidin-horseradish peroxidase histochemistry. The pore size of the zonulae adherentes that collectively comprise the external limiting membrane has been found to lie between 30 and 36A. This is sufficiently small to block passage of interstitial retinol-binding protein (IRBP, Stokes' radius = 55A) from the interstitial space vitread into the retina. IRBP has been localized to the interstitial space of bovine retina by use of indirect immunogold electron microscopy. IRBP has also been identified in cytoplasmic vesicles of rod and cone inner segments. The function of these vesicles may be for secretion and/or uptake of IRBP from the interstitial space. A postulated function of IRBP is transfer of vitamin A between the retinal pigment epithelium and photoreceptors during the visual cycle. Biochemical experiments have corroborated previous studies that IRBP becomes loaded with all-trans-retinol following bleaching illumination, while the amount of endogenous 11-cis-retinol remains unchanged. These data are consistent with the emerging concept that IRBP plays a role in transport of vitamin A among the cell types that border the interstitial space.
已使用免疫细胞化学和生化技术对间质空间进行了表征。利用一系列已知斯托克斯半径的生物素化蛋白质，随后进行抗生物素蛋白 - 辣根过氧化物酶组织化学，探测了形成该细胞外空间玻璃体边缘的外界膜的孔径。已发现共同构成外界膜的紧密连接带的孔径在30至36埃之间。这足够小，可阻止间质视黄醇结合蛋白（IRBP，斯托克斯半径 = 55埃）从玻璃体间质空间进入视网膜。通过间接免疫金电子显微镜已将IRBP定位到牛视网膜的间质空间。在视杆和视锥细胞内段的细胞质小泡中也鉴定出了IRBP。这些小泡的功能可能是用于从间质空间分泌和/或摄取IRBP。IRBP的一个假定功能是在视觉循环期间在视网膜色素上皮和光感受器之间转移维生素A。生化实验证实了先前的研究，即漂白光照后IRBP会负载全反式视黄醇，而内源性11 - 顺式视黄醇的量保持不变。这些数据与IRBP在与间质空间相邻的细胞类型之间的维生素A运输中起作用这一新兴概念一致。
