Kennedy A, Frank R N
Kresge Eye Institute, Wayne State University, School of Medicine, Detroit, Michigan 48201.
Invest Ophthalmol Vis Sci. 1993 Mar;34(3):547-58.
The authors previously reported that a diet containing 30% galactose retards the development of the late-onset photoreceptor dystrophy in the spontaneously hypertensive (SHR) rat. It was suggested that the dystrophy might result from faulty galactosylation of a critical glycoprotein or glycosaminoglycan (GAG) in the interphotoreceptor matrix (IPM). In the current study, this hypothesis was tested by studying IPM protein and GAG composition in SHR and normotensive Wistar-Kyoto (WKy) control strain rats fed a standard or a high-galactose (30%) diet.
The authors performed biochemical analyses of the IPM of SHR and of WKy control rats fed either the basal diet or a 30% galactose diet for 14 mo and labeled at the termination of the experiment with 3H-glucosamine and 35S-sulfate. Analyses included high-performance liquid chromatography and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) of extracted proteoglycans with identification of the GAG by selective enzymatic degradation and immunoblotting of SDS-PAGE gels for interphotoreceptor retinol-binding protein (IRBP), with slot blots for additional quantitation.
Although several differences were detected in GAG radiolabeling between the two strains, only one, a decreased overall synthesis of 3H-glucosamine-labeled GAG in the WKy rats, was altered by the high-galactose diet. There was no apparent difference in the protein patterns of the IPM as evaluated by two-dimensional SDS-PAGE and IEF. However, slot blots of that portion of the IPM extracted from the neural retinas showed less reactivity per microgram of protein for IRBP in the galactose-fed animals of both strains than for the rats fed a basal diet. This was statistically significant, however, only in the WKy rats.
The composition of the IPM of these two strains of rat appears similar to the composition of the IPM of other species that have been studied. Whether the quantitative alteration in IRBP that appears to be produced by galactose feeding has functional significance, with particular relevance to retarding the development of the photoreceptor cell dystrophy of the SHR rat, is unclear at this time.
作者之前报道，含30%半乳糖的饮食可延缓自发性高血压（SHR）大鼠迟发性光感受器营养不良的发展。有人认为，这种营养不良可能是由于光感受器间基质（IPM）中关键糖蛋白或糖胺聚糖（GAG）的半乳糖基化缺陷所致。在本研究中，通过研究喂食标准或高半乳糖（30%）饮食的SHR大鼠和正常血压的Wistar-Kyoto（WKy）对照品系大鼠的IPM蛋白和GAG组成，对这一假设进行了验证。
作者对喂食基础饮食或30%半乳糖饮食14个月并在实验结束时用3H-葡萄糖胺和35S-硫酸盐标记的SHR大鼠和WKy对照大鼠的IPM进行了生化分析。分析包括高效液相色谱、二维十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）和提取的蛋白聚糖的等电聚焦（IEF），通过选择性酶降解鉴定GAG，并对SDS-PAGE凝胶进行免疫印迹以检测光感受器间视黄醇结合蛋白（IRBP），用狭缝印迹进行额外定量。
虽然在两种品系的GAG放射性标记方面检测到了一些差异，但只有一种差异，即WKy大鼠中3H-葡萄糖胺标记的GAG的总体合成减少，会因高半乳糖饮食而改变。通过二维SDS-PAGE和IEF评估，IPM的蛋白质模式没有明显差异。然而，从神经视网膜提取的IPM部分的狭缝印迹显示，两种品系中喂食半乳糖的动物每微克蛋白质的IRBP反应性均低于喂食基础饮食的大鼠。不过，这仅在WKy大鼠中具有统计学意义。
这两种品系大鼠的IPM组成似乎与已研究的其他物种的IPM组成相似。目前尚不清楚半乳糖喂养似乎产生的IRBP定量改变是否具有功能意义，特别是与延缓SHR大鼠光感受器细胞营养不良的发展是否相关。
