Intracellular topography of rhodopsin regeneration in vertebrate rods.

Williams TP, Penn JS
J Gen Physiol. 1985 86 (3): 413-22

PMID: 4056732 · PMCID: PMC2228799 · DOI:10.1085/jgp.86.3.413

The vertebrate visual pigment of rods, rhodopsin, bleaches in light and regenerates in darkness. When the bleaching and regeneration are carried out in vivo, it is found that the regeneration takes place at nonuniform rates along the rod outer segment (ROS): toads and frogs regenerate rhodopsin faster in the proximal ends of the ROS than in the distal ends. Rats do the reverse. These patterns of regeneration persist whether the bleaching is done with flashes or with steady light. They are also independent of the extent to which the retinal pigment epithelium contains melanin. Furthermore, the dichotomy of patterns (proximal faster vs. distal faster) does not seem to depend upon the presence of an excess of stored retinoid in the eye. Instead, it is suggested that the villous processes of the epithelial cells may play an important role in the regeneration patterns. These processes in amphibia extend nearly to the rod inner segment but in the rat they surround only the apical end of the outer segment. If they "funnel" the retinoids back to the ROS, their location and morphology could explain the two different kinds of patterns seen.

MeSH Terms (12)

Animals Anura Intracellular Membranes Photoreceptor Cells Pigment Epithelium of Eye Rabbits Rats Rats, Inbred Strains Retinal Pigments Rhodopsin Rod Cell Outer Segment Tissue Distribution

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