Ultimate fate of rod outer segments in the retinal pigment epithelium

To investigate the degradation pathway of rod outer segments (ROS) in vivo, we injected gold-labeled ROS into the subretinal space of rabbits using a pars plana approach. Histology and electron microscopy performed on the spe cimens 72 hr after ROS injection revealed that the retina over the injectio n site was reattached, the retinal pigment epithelial (RPE) cells were inta ct, and gold granules were localized inside melanin granules and melanosome s. These results indicate that, in RPE, in vivo degradation of ROS is assoc iated with melanosomes.