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Felicity Bowers, Krisztina Valter, Suwei Chan, Natalie Walsh, Juliani Maslim, Jonathan Stone; Effects of Oxygen and bFGF on the Vulnerability of Photoreceptors to Light Damage. Invest. Ophthalmol. Vis. Sci. 2001;42(3):804-815.
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purpose. To test whether tissue oxygen levels affect the vulnerability of
photoreceptors to damage by bright continuous light (BCL).
methods. Albino rats were raised in standard conditions of cyclic light (12-hour
light, 12-hour darkness) with the light level at 5 to 10 lux or 40 to
65 lux. They were then exposed to BCL (1000–1400 lux), either
continuously for 48 hours or for the day or night components of the
48-hour period. During BCL, some rats were kept in room air (normoxia,
21% oxygen), some in hypoxia (10%), and some in hyperoxia (70%).
Their retinas were examined for cell death, for the expression of basic
fibroblast growth factor (bFGF), and for response to light
results. The death of retinal cells induced by BCL was confined to
photoreceptors. Within the retina, the severity of death was inversely
related to the level of bFGF immunolabeling in the somas of the outer
nuclear layer (ONL) before exposure. The death of photoreceptors was
accompanied by an upregulation of bFGF protein levels in the ONL and by
a decline in the ERG. Both hypoxia and hyperoxia during BCL reduced the
photoreceptor death, bFGF upregulation, and ERG decline caused by BCL.
The protective effects of hyperoxia and hypoxia were evident during
both the day and night halves of the daily cycle. Hypoxia or hyperoxia
alone did not upregulate bFGF or ciliary neurotrophic factor (CNTF)
expression in the retina.
conclusions. Photoreceptors are protected from light damage by hypoxia and hyperoxia
during exposure. The protection provided by oxygen levels operates
during both day and night. The protection is not mediated by an
upregulation of bFGF or CNTF.
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