title: Localization of retinal "48K" (S-antigen) by electron microscopy.
abstract: The subcellular localization of the 48-kDa protein, a soluble protein in rod photoreceptors that is identical to retinal S-antigen, has been examined in photoreceptors of the toad (Bufo marinus) by immunoelectron microscopy. Pairs of retinas, exposed to controlled conditions of light- and dark-adaptation were compared. Lowicryl-embedded sections of light-adapted versus dark-adapted retinas were incubated with polyclonal anti-48K antibodies, then post-treated with second antibodies that were conjugated with 5 nm gold particles. In dark-adapted rod photoreceptors, the highest labeling density (approximately 39 gold particles/micron2) was found in the myoid region of the inner segment. Light-adaptation significantly affected the pattern of labeling. The principal change was a two-fold increase in labeling density in the basal region of the outer segment; this was accompanied by a decrease in labeling density in the myoid region. Labeling densities in the other subcellular compartments examined ranged from 7-10 gold particles/micron2; these densities did not differ substantially between light- versus dark-adapted preparations.
mesh_terms: D000221:Adaptation, Ocular; D000818:Animals; D000941:Antigens / Q000032:analysis*; D019393:Arrestin; D002024:Bufo marinus; D005136:Eye Proteins / Q000032:analysis*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000648:ultrastructure*
chemical_list: D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins