Williams T P
J Gen Physiol. 1984 Jun;83(6):841-52. doi: 10.1085/jgp.83.6.841.
Rod photoreceptors renew the membranous disks of the outer segments (ROS). New disks are assembled at the proximal base and old disks are shed at the distal tip. Rhodopsin, the major protein of the disk, remains with the disk into which it was inserted. Thus, it is true that the oldest rhodopsin is at the tip and the newest at the base. A microspectrophotometer is used to examine the properties of rhodopsin in the two ends of the toad ROS. No differences between the two are found in absorption spectrum, concentration, dichroism, photoconversion rates, or lateral diffusion rates. Regeneration of rhodopsin from the bleached state is also studied but cannot be used to discriminate old from new rhodopsin because the point of entry of regeneration retinoids and/or their concentrations cannot be controlled. However, a new insight into pigment regeneration in the living toad eye is gained: regeneration is faster in the basal disks than in the distal.
视杆光感受器会更新其外段（ROS）的膜盘。新的膜盘在近端基部组装，而旧的膜盘则在远端顶端脱落。视紫红质是膜盘的主要蛋白质，它会随着其插入的膜盘一起保留。因此，最老的视紫红质确实在顶端，而最新的在基部。使用显微分光光度计来检测蟾蜍视杆外段两端视紫红质的特性。在吸收光谱、浓度、二向色性、光转换速率或横向扩散速率方面，两端之间未发现差异。还对视紫红质从漂白状态的再生进行了研究，但由于再生视黄醛的进入点和/或其浓度无法控制，所以不能用于区分新旧视紫红质。然而，对活体蟾蜍眼中色素再生有了新的认识：基部膜盘中的再生比远端更快。
