Prevention of rod disk shedding by detachment from the retinal pigment epithelium

The authors tested whether or not rod outer segment (ROS) disks are shed when the neural retina is detached from the retinal pigment epithelium (RPE). Adult Xenopus were injected with 3H-L-leucine. Later, when the distal disks of their ROSs were labeled with a band of 3H-leucine, their eyes were enucleated. Intact eyecups, eyecups with partially detached retinae, and retinae that were peeled completely away from the RPE were incubated in culture medium. Disk shedding was stimulated by changes in lighting, or the addition of 0.5 mM ouabain. Where the retina was attached, phagosomes in the RPE, and not the ROSs, contained most of the radiolabel. Where there was retinal detachment, ROSs were still heavily radiolabeled near their distal ends. It was concluded that mechanical retinal detachment prevents ROS disk shedding.