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Izhak Nir, Joseph M. Harrison, Changdong Liu, Rong Wen; Extended Photoreceptor Viability by Light Stress in the RCS Rats but not in the Opsin P23H Mutant Rats. Invest. Ophthalmol. Vis. Sci. 2001;42(3):842-849.
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purpose. To determine the effect of light stress on retinal function and long-term
photoreceptor viability in Royal College of Surgeons (RCS) rats and the
applicability of the light treatment to the opsin P23H mutant rats.
methods. RCS rats at postnatal day (P)23 were illuminated with 120 foot-candles
(fc) white light for 10 hours. Photoreceptor survival and basic
fibroblast growth factor (bFGF) expression were measured at P60 and
P83. Retinal function was evaluated by electroretinography. Opsin P23H
transgenic rats were treated with light at P28 and analyzed at P70 for
photoreceptor viability, ultrastructure, and bFGF expression.
results. Light-treated RCS rats at P60 had four to five rows of nuclei versus
one to two rows in untreated littermates. The average amplitude of the
ERG b-wave was 28 μV in treated rats, compared with 6 μV in
untreated littermates. By P83 there was still significant preservation
of the ONL in treated rats. Immunoblot analysis showed a high
expression of bFGF in the treated retinas even 2 months after
treatment. Illumination of P23H rats at P28 with 120 fc white light for
10 hours caused substantial photoreceptor cell death, although bFGF
expression was upregulated. Lowered illumination dosages continued to
cause photoreceptor damage until levels were reached that neither
caused damage nor enhanced survival.
conclusions. Although light stress promotes photoreceptor survival and function in
the RCS rat, it elicits death signals in the P23H rats that may not be
overcome by survival-promoting factors. Therefore, use of light stress
to promote photoreceptor survival should be considered with regard to
sensitivity of the mutation to light damage.
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