Carter-Dawson L, Kuwabara T, O'Brien P J, Bieri J G
Invest Ophthalmol Vis Sci. 1979 May;18(5):437-46.
The levels of rhodopsin and opsin were investigated in relation to the maintenance of retinal structure in retinas of vitamin A--deficient rats in low levels of cyclic illumination (1.5 to 2 foot-candles). Rhodopsin levels decreased in the deficient retinas to approximately 20% of control at 9 weeks, and this level was retained through 39 weeks on the deficient diet. Opsin levels decreased at a slower rate but reached about 20% of control levels at 32 weeks. Despite the decrease in rhodopsin levels, obvious deterioration of disc structure was not observed until 16 weeks of deficiency, when opsin levels had already decreased to 60% to 70% of control. The structural disruption of photoreceptor outer segments was localized initially in discs of the distal third. Rod cell degeneration preceded cone cell degeneration in vitamin A--deficient retinas. Most of the rods and cones persisted in the posterior retina at 23 weeks on the deficient diet; however, by 40 weeks, only 11% of the rod nuclei remained. In contrast, about 63% of the cone nuclei were present at 40 weeks of deficiency. The photoreceptor cells were affected by the deficiency to a greater extent in the inferior hemisphere than in the superior hemisphere of the eye.
研究了在低强度周期性光照（1.5至2英尺烛光）下，维生素A缺乏大鼠视网膜中视紫红质和视蛋白水平与视网膜结构维持之间的关系。在缺乏维生素A的视网膜中，视紫红质水平在9周时降至对照组的约20%，并在缺乏维生素A的饮食喂养39周期间一直保持这一水平。视蛋白水平下降速度较慢，但在32周时降至对照组水平的约20%。尽管视紫红质水平下降，但直到缺乏维生素A 16周时才观察到明显的盘状结构恶化，此时视蛋白水平已降至对照组的60%至70%。光感受器外段的结构破坏最初局限于远端三分之一的盘状结构。在维生素A缺乏的视网膜中，杆状细胞变性先于锥状细胞变性。在缺乏维生素A的饮食喂养23周时，大多数杆状细胞和锥状细胞仍存在于视网膜后部；然而，到40周时，仅11%的杆状细胞核留存。相比之下，在缺乏维生素A 40周时，约63%的锥状细胞核仍存在。眼的下半球光感受器细胞受缺乏维生素A的影响程度大于上半球。
