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Reduced rate of rod outer segment disk synthesis in photoreceptor cells recovering from UVA light damage.

Abstract

PURPOSE

Recovery of photoreceptor cells after light damage is thought to involve the physiologic process of disk renewal. However, only indirect evidence is available to support this hypothesis. The present study sought to examine more directly the mechanisms of photoreceptor cell recovery by quantitatively assessing the rate of rod outer segment (ROS) disk synthesis in retinas damaged by ultraviolet-A (UVA) light.

METHODS

Pigmented rats were anesthetized, and their right eyes were exposed for 1 hour to a uniform field of UVA light at a dose of 6 J/cm2. Animals were returned to their dim cyclic light environment and were allowed to recover for various time points up to 42 days, at which time their eyes were enucleated for histologic examination and quantification of outer nuclear layer (ONL) thickness. Seven days before the 6- and 21-day time points, some animals were intravitreally injected with 3H-leucine in both eyes, and these eyes were used to analyze autoradiographically the rate of ROS disk synthesis.

RESULTS

ROS disk synthesis in UVA-exposed eyes was 43% slower relative to nonexposed controls in the more severely damaged superior retina at postexposure day 6. Ultrastructural observations revealed a sharp demarcation between damaged and recovered ROS disks at this time. At postexposure day 21, there was a marked recovery in outer segment structure despite a further decrease in ONL thickness and a continued slow rate of disk synthesis. In the less severely damaged inferior region of the retina, the rate of disk synthesis was not altered by UVA exposure, although mild ROS disruption was evident at the earlier time points.

CONCLUSIONS

These findings indicate that the rate of ROS disk synthesis is slowed in moderately damaged photoreceptor cells even though they eventually fully recover in structure. A slow-down of this rate after UVA exposure may be an adaptive change geared toward recovery mechanisms, or it may simply be a manifestation of cellular damage.

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  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030.

    ,

    Source

    MeSH

    Animals
    Autoradiography
    Female
    Leucine
    Light
    Photoreceptor Cells
    Radiation Injuries, Experimental
    Rats
    Rats, Sprague-Dawley
    Retina
    Rod Cell Outer Segment
    Ultraviolet Rays

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't
    Research Support, U.S. Gov't, P.H.S.

    Language

    eng

    PubMed ID

    8056530

    Citation

    Rapp, L M., et al. "Reduced Rate of Rod Outer Segment Disk Synthesis in Photoreceptor Cells Recovering From UVA Light Damage." Investigative Ophthalmology & Visual Science, vol. 35, no. 9, 1994, pp. 3540-8.
    Rapp LM, Fisher PL, Dhindsa HS. Reduced rate of rod outer segment disk synthesis in photoreceptor cells recovering from UVA light damage. Invest Ophthalmol Vis Sci. 1994;35(9):3540-8.
    Rapp, L. M., Fisher, P. L., & Dhindsa, H. S. (1994). Reduced rate of rod outer segment disk synthesis in photoreceptor cells recovering from UVA light damage. Investigative Ophthalmology & Visual Science, 35(9), pp. 3540-8.
    Rapp LM, Fisher PL, Dhindsa HS. Reduced Rate of Rod Outer Segment Disk Synthesis in Photoreceptor Cells Recovering From UVA Light Damage. Invest Ophthalmol Vis Sci. 1994;35(9):3540-8. PubMed PMID: 8056530.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Reduced rate of rod outer segment disk synthesis in photoreceptor cells recovering from UVA light damage. AU - Rapp,L M, AU - Fisher,P L, AU - Dhindsa,H S, PY - 1994/8/1/pubmed PY - 1994/8/1/medline PY - 1994/8/1/entrez SP - 3540 EP - 8 JF - Investigative ophthalmology & visual science JO - Invest. Ophthalmol. Vis. Sci. VL - 35 IS - 9 N2 - PURPOSE: Recovery of photoreceptor cells after light damage is thought to involve the physiologic process of disk renewal. However, only indirect evidence is available to support this hypothesis. The present study sought to examine more directly the mechanisms of photoreceptor cell recovery by quantitatively assessing the rate of rod outer segment (ROS) disk synthesis in retinas damaged by ultraviolet-A (UVA) light. METHODS: Pigmented rats were anesthetized, and their right eyes were exposed for 1 hour to a uniform field of UVA light at a dose of 6 J/cm2. Animals were returned to their dim cyclic light environment and were allowed to recover for various time points up to 42 days, at which time their eyes were enucleated for histologic examination and quantification of outer nuclear layer (ONL) thickness. Seven days before the 6- and 21-day time points, some animals were intravitreally injected with 3H-leucine in both eyes, and these eyes were used to analyze autoradiographically the rate of ROS disk synthesis. RESULTS: ROS disk synthesis in UVA-exposed eyes was 43% slower relative to nonexposed controls in the more severely damaged superior retina at postexposure day 6. Ultrastructural observations revealed a sharp demarcation between damaged and recovered ROS disks at this time. At postexposure day 21, there was a marked recovery in outer segment structure despite a further decrease in ONL thickness and a continued slow rate of disk synthesis. In the less severely damaged inferior region of the retina, the rate of disk synthesis was not altered by UVA exposure, although mild ROS disruption was evident at the earlier time points. CONCLUSIONS: These findings indicate that the rate of ROS disk synthesis is slowed in moderately damaged photoreceptor cells even though they eventually fully recover in structure. A slow-down of this rate after UVA exposure may be an adaptive change geared toward recovery mechanisms, or it may simply be a manifestation of cellular damage. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/8056530/Reduced_rate_of_rod_outer_segment_disk_synthesis_in_photoreceptor_cells_recovering_from_UVA_light_damage_ L2 - http://iovs.arvojournals.org/article.aspx?volume=35&page=3540 DB - PRIME DP - Unbound Medicine ER -