Fröhlich E, Klessen C
Anatomisches Institut der Eberhard-Karls-Universität, Tübingen, Germany.
Graefes Arch Clin Exp Ophthalmol. 2001 Jan;239(1):25-34. doi: 10.1007/s004170000218.
The retinal pigment epithelium (RPE) contains a variety of enzymes that are involved in the metabolism of the neural retina. It has been shown that the photoreceptor densities display regional variations. We aimed to find out whether the enzymes in the RPE also display regional differences.
Various enzymes were localized in RPE cells in situ and in cultured RPE cells. RPE cells of the entire tapetal region of adult and fetal bovine eyes were examined. The following enzymes were studied: Activities of aminopeptidases A and M, dipeptidylpeptidases I and II, and gamma-glutamyltranspeptidase were localized by histochemistry. Alkaline phosphatase, dipeptidylpeptidase IV, and cathepsin B were studied by histochemistry and immunocytochemistry. In addition, activities of two enzymes were localized in one cell.
The distribution pattern of the enzymatic activities showed no marked regional differences. In contrast, pronounced cell-to-cell variability in the activities was detected for some of the enzymes tested. These intercellular differences were detected already in fetal retinae of early stages and persisted in RPE cultures.
The heterogeneous distribution of enzymatic activities in RPE cells appears not to be caused exclusively by stimuli from the neural retina and from the choroid, because heterogeneity starts in the early fetal period and persists in culture.
视网膜色素上皮（RPE）含有多种参与神经视网膜代谢的酶。研究表明，光感受器密度存在区域差异。我们旨在探究RPE中的酶是否也存在区域差异。
在原位和培养的RPE细胞中定位各种酶。检查成年和胎儿牛眼整个绒毡层区域的RPE细胞。研究了以下酶：通过组织化学定位氨肽酶A和M、二肽基肽酶I和II以及γ-谷氨酰转肽酶的活性。通过组织化学和免疫细胞化学研究碱性磷酸酶、二肽基肽酶IV和组织蛋白酶B。此外，在一个细胞中定位了两种酶的活性。
酶活性的分布模式未显示出明显的区域差异。相反，对于一些测试的酶，检测到活性存在明显的细胞间变异性。这些细胞间差异在早期胎儿视网膜中就已检测到，并在RPE培养物中持续存在。
RPE细胞中酶活性的异质性分布似乎并非仅由神经视网膜和脉络膜的刺激引起，因为异质性在胎儿早期就已开始并在培养中持续存在。
