Bush R A, Remé C E, Malnoë A
Department of Ophthalmology, University of Zürich, Switzerland.
Exp Eye Res. 1991 Dec;53(6):741-52. doi: 10.1016/0014-4835(91)90109-r.
We investigated the effect of depleting membrane docosahexaenoic acid (DHA, 22:6n-3) content through dietary deprivation of n-3 fatty acids on the susceptibility of the photoreceptors and pigment epithelium cells to acute light-induced changes. Male Sprague-Dawley rats were raised throughout gestation, lactation and up to the age of 8 weeks on semi-purified diets containing either safflower oil (SFO, n-3 deficient diet) or soybean oil (SO) as the sole source of lipids. A third group was switched at weaning from safflower oil to soybean oil (SFO/SO). Rats were maintained on a 12 hr/12 hr light/dark cycle in which the light level at the front of the cages was 5-10 lx. Light damage was produced by exposing dark-adapted animals to diffuse white fluorescent light of 700-800 lx for 30 min followed by 90 min of darkness. In order to study recovery from light damage, additional groups of SFO and SO rats were returned to dim cyclic light for 27 hr following bright light exposure. DHA content in retinal phosphatidylethanolamine and phosphatidylcholine was 65-75% lower in rats fed SFO than in rats fed SO. The decrease was compensated for by an increase in 22:5n-6, the total content of polyunsaturated fatty acids (PUFA) being similar in both the SFO and SO groups. The SFO/SO rats had DHA levels similar to SO animals, but 22:5n-6 remained elevated resulting in a slightly higher level of total PUFA. Severe rod outer segment (ROS) membrane disruptions were seen following bright light exposure in rats on the SO and SFO/SO diets. The appearance of these disruptions did not change significantly during more than 24 hr in dim cyclic light. In contrast, there were virtually no acute ROS lesions in the SFO group. Furthermore, there was a strong light-elicited disk-shedding response in the SO rats but not in the other two groups. The pigment epithelium of the DHA deficient retinas showed a significantly greater accumulation of large lipid droplets in the dark-adapted state. Notably, whole retina rhodopsin levels were 15% higher in the SFO than in the SO group. These results indicate that depletion of retinal DHA reduces the susceptibility of the rod outer segments to acute light damage and at the same time may alter visual pigment photochemistry and other photoreceptor and pigment epithelium functions.
我们研究了通过饮食中缺乏n-3脂肪酸来降低膜二十二碳六烯酸（DHA，22:6n-3）含量，对光感受器和色素上皮细胞对急性光诱导变化的易感性的影响。雄性Sprague-Dawley大鼠在整个妊娠期、哺乳期直至8周龄，均饲养在以红花油（SFO，n-3缺乏饮食）或大豆油（SO）作为唯一脂质来源的半纯化饮食中。第三组在断奶时从红花油换成大豆油（SFO/SO）。大鼠维持在12小时光照/12小时黑暗的循环光照周期中，笼前的光照强度为5-10勒克斯。通过将暗适应的动物暴露于700-800勒克斯的漫射白色荧光下30分钟，随后黑暗90分钟来产生光损伤。为了研究光损伤后的恢复情况，在强光暴露后，将另外几组SFO和SO大鼠放回昏暗的循环光照下27小时。喂食SFO的大鼠视网膜磷脂酰乙醇胺和磷脂酰胆碱中的DHA含量比喂食SO的大鼠低65-75%。这种减少被22:5n-6的增加所补偿，SFO组和SO组的多不饱和脂肪酸（PUFA）总含量相似。SFO/SO大鼠的DHA水平与SO组动物相似，但22:5n-6仍然升高，导致总PUFA水平略高。在喂食SO和SFO/SO饮食的大鼠中，强光暴露后可见严重的视杆外段（ROS）膜破坏。在昏暗的循环光照下超过24小时，这些破坏的外观没有明显变化。相比之下，SFO组几乎没有急性ROS损伤。此外，SO大鼠有强烈的光诱导盘状脱落反应，而其他两组则没有。DHA缺乏视网膜的色素上皮在暗适应状态下显示出明显更多的大脂滴积累。值得注意的是，SFO组的全视网膜视紫红质水平比SO组高15%。这些结果表明，视网膜DHA的消耗降低了视杆外段对急性光损伤的易感性，同时可能改变视觉色素光化学以及其他光感受器和色素上皮功能。
