Bush R A, Malnoë A, Remé C E, Williams T P
Department of Ophthalomology, University of Zürich, Switzerland.
Invest Ophthalmol Vis Sci. 1994 Jan;35(1):91-100.
To investigate the possibility that previously demonstrated reductions in photoreceptor sensitivity to light in n-3 fatty-acid-deficient rats can be explained by alterations in rhodopsin content and/or function.
Sprague-Dawley rats were reared throughout gestation, lactation, and up to 24 weeks of age on a diet containing safflower oil (n-3 fatty-acid-deficient) or soybean oil as the sole source of lipids. Dark-adapted content and in vivo regeneration of rhodopsin after bleaching were measured by detergent extraction. The regeneration rate constants and number of photons absorbed by rhodopsin under steady-state bleach conditions were calculated from these values. The rate of metarhodopsin II (MII) formation in vitro was determined by flash bleaching extracted pigment and native rod outer segment membranes. Rod outer segment length and photoreceptor cell density were determined in histologic sections through the inferior central retina.
Dark-adapted rhodopsin content of retinas from rats reared on safflower oil was 12% to 15% higher than that of rats raised on soybean oil at every age measured. The rate of rhodopsin regeneration was significantly slower in rats reared on safflower oil while the level of steady-state bleach was the same. This meant that the rats reared on safflower oil absorbed about one half as many photons during light exposure. The rate of metarhodopsin II formation in vitro was unaffected by n-3 fatty acid deficiency. No difference in either rod outer segment length or cell number was detected.
A reduced capacity for photon absorption by rhodopsin could play a role in lowering retinal sensitivity to light in n-3 fatty-acid-deficient rats.
探讨能否用视紫红质含量和/或功能的改变来解释先前在n-3脂肪酸缺乏的大鼠中所证实的光感受器对光敏感性降低的现象。
在整个妊娠期、哺乳期直至24周龄，将斯普拉格-道利大鼠饲养在以红花油（n-3脂肪酸缺乏）或大豆油作为唯一脂质来源的饮食中。通过去污剂提取法测量暗适应状态下视紫红质的含量以及漂白后视紫红质的体内再生情况。根据这些值计算稳态漂白条件下视紫红质的再生速率常数和吸收的光子数。通过对提取的色素和天然视杆外段膜进行闪光漂白来测定体外视紫红质II（MII）的形成速率。通过对视网膜中央下部的组织切片进行检测，确定视杆外段长度和光感受器细胞密度。
在每个测量年龄，以红花油饲养的大鼠视网膜暗适应视紫红质含量比以大豆油饲养的大鼠高12%至15%。以红花油饲养的大鼠视紫红质再生速率明显较慢，而稳态漂白水平相同。这意味着以红花油饲养的大鼠在光照期间吸收的光子数约为以大豆油饲养的大鼠的一半。n-3脂肪酸缺乏对视紫红质II在体外的形成速率没有影响。未检测到视杆外段长度或细胞数量的差异。
视紫红质吸收光子的能力降低可能在n-3脂肪酸缺乏的大鼠视网膜对光敏感性降低中起作用。
