Penn J S, Williams T P
Exp Eye Res. 1986 Dec;43(6):915-28. doi: 10.1016/0014-4835(86)90070-9.
Albino rats were born and raised in 12 hr light: 12 hr dark regimes of illuminances varying from 3- to 800 lx. At 15 weeks of age, the animals were killed and determinations were made of the following: dark-adapted and steady-state rhodopsin levels; rod outer-segment length and photoreceptor-cell density; retinal topography of rhodopsin absorbance, and regeneration rate of visual pigment in vivo. It was found that there is a four-fold drop in the dark-adapted rhodopsin level of animals raised in 400-lx cyclic light compared with those raised in 3 lx. This difference can be accounted for by differences in rod outer-segment length and transverse absorbance of frozen retinal sections. Further, this change in rhodopsin content, coupled with variations in the visual pigment regeneration rate, allows the rat to control the amount of pigment in its retina at steady-state bleach. In this way, the rat can regulate the number of photons its retina catches each day. Animals raised in cyclic illuminances differing by more than two orders of magnitude catch very nearly equal number of photons (1.10 +/- 0.2 X 10(16) per eye) during the light period. A reduction in the number of photoreceptor cells also occurs with increasing illuminance, and these changes are more pronounced in the inferior region of the retina. This is not typical of the type of light-induced retinal damage caused by acute exposures.
白化大鼠在光照强度为3至800勒克斯、12小时光照：12小时黑暗的条件下出生并饲养。在15周龄时，将动物处死并进行以下测定：暗适应和稳态视紫红质水平；视杆外段长度和光感受器细胞密度；视紫红质吸光度的视网膜地形图，以及体内视觉色素的再生率。结果发现，与饲养在3勒克斯环境中的动物相比，饲养在400勒克斯循环光照下的动物暗适应视紫红质水平下降了四倍。这种差异可以通过视杆外段长度和冷冻视网膜切片的横向吸光度的差异来解释。此外，视紫红质含量的这种变化，再加上视觉色素再生率的变化，使得大鼠能够在稳态漂白时控制其视网膜中的色素量。通过这种方式，大鼠可以调节其视网膜每天捕获的光子数量。饲养在光照强度相差两个数量级以上的循环光照下的动物，在光照期间捕获的光子数量几乎相等（每只眼睛1.10±0.2×10¹⁶个）。随着光照强度的增加，光感受器细胞的数量也会减少，并且这些变化在视网膜的下部区域更为明显。这不是急性暴露引起的光诱导视网膜损伤类型的典型表现。
