STUDIES ON FINE STRUCTURE AND RHODOPSIN CYCLE OF RABBIT RETINA IN EXPERIMENTAL DEGENERATION INDUCED BY SODIUM IODATE
STUDIES ON FINE STRUCTURE AND RHODOPSIN CYCLE OF RABBIT RETINA IN EXPERIMENTAL DEGENERATION INDUCED BY SODIUM IODATE
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DOI：
10.1016/s0014-4835(66)80024-6
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发表时间：
1966-01-01
影响因子：
3.4
通讯作者：
CALABRIA, GA
中科院分区：
文献类型：
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作者：
GRIGNOLO, A;ORZALESI, N;CALABRIA, GA
本文观察了实验性碘酸钠变性兔视网膜的超微结构和视紫红质循环。第一个超微结构的变化中观察到的色素上皮细胞，其细胞表现出早期和严重的参与，在几天内完全破坏结束。色素上皮损伤后，Muller细胞外侧肿胀，视细胞外节变性。在治疗的晚期，变性的色素上皮细胞被修饰的色素细胞所取代。这些新细胞具有独特的细胞学特征，并对感光细胞外节和破裂的色素细胞的碎片具有显著的吞噬活性。在光适应和暗适应条件下处理的动物中出现了类似的退行性变化。然而，在光适应的兔子中，视紫红质测量显示用碘酸钠处理的视网膜中的视紫红质浓度早期降低，而在暗适应的兔子中，记录到正常水平的视紫红质。这表明，视网膜色素上皮细胞的变性可以阻止视紫红质的再合成过程中的光适应条件。这一建议支持了以下假设：视紫红质循环的重要过程，特别是维生素A和视黄烯的异构化，只能在视网膜层中进行。此外，光感受器外节的变性总是伴随着色素上皮的严重损伤，这一事实可能表明视细胞对色素细胞存在某种营养依赖性。实验性视网膜变性作为研究视网膜功能的新工具，具有重要意义。事实上，代谢毒物影响不同视网膜层的选择性方式允许人们评估这些层中的阻断活性所引起的形态和功能效应。
The authors investigated the ultrastructure and the rhodopsin cycle of the rabbit retina by experimental degeneration with sodium iodate. The first ultrastructural changes were observed in the pigment epithelium, whose cells showed early and severe involvement ending in complete destruction within a few days. A swelling of the outer side of the Muller cells and the degeneration of the outer segments of the visual cells followed the damage to the pigment epithelium. In the advanced stages of the treatment, the degenerated cells of the pigment epithelium were replaced by modified pigment cells. These new cells had peculiar cytological features and marked phagocytic activity toward fragments of the outer segments of the photoreceptors and of the disrupted pigmented cells. Similar degenerative changes developed in the animals treated under conditions of light and dark adaptation. In the light-adapted rabbits, however, the rhodopsin measurements revealed an early decrease of the rhodopsin concentration in the retinas treated with sodium iodate, whereas in the dark-adapted rabbits, normal levels of the photopigment were recorded. It is suggested, therefore, that the degeneration of the retinal pigment epithelium could block the process of resynthesis of the rhodopsin under light-adaptation conditions. This suggestion supports the hypothesis that important processes of the rhodopsin cycle, specifically the isomerization of vitamin A and of retinene, can be performed only in this retinal layer. Moreover, the fact that the degeneration of the outer segments of photoreceptors always followed severe damage to the pigment epithelium may indicate the existence of some nutritional dependence of the visual cells on the pigmented ones. The experimental degeneration of the retina as a new tool for studying the retinal function is of great importance. In fact, the selective manner in which metabolic poisons affect the different retinal layers allows one to evaluate the morphological and functional effects caused by the blocking activity in these layers.