Effects of Oxygen and bFGF on the Vulnerability of Photoreceptors to Light Damage

• Published in: Investigative ophthalmology & visual science Vol. 42; no. 3; pp. 804 - 815
• Main Authors: Bowers, Felicity, Valter, Krisztina, Chan, Suwei, Walsh, Natalie, Maslim, Juliani, Stone, Jonathan
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01-03-2001; Association for Research in Vision and Ophtalmology
• Subjects: Animals; Biological and medical sciences; Blood Gas Analysis; Cell Death; Ciliary Neurotrophic Factor - metabolism; Circadian Rhythm; Electroretinography; Fibroblast Growth Factor 2 - metabolism; Hyperoxia - metabolism; Hypoxia - metabolism; In Situ Nick-End Labeling; Injuries of the orbit. Foreign bodies of the eye. Diseases due to physical agents; Light - adverse effects; Medical sciences; Oxygen - physiology; Photoreceptor Cells, Vertebrate - radiation effects; Radiation Injuries, Experimental - etiology; Radiation Injuries, Experimental - metabolism; Radiation Injuries, Experimental - prevention & control; Rats; Rats, Sprague-Dawley; Retinal Diseases - etiology; Retinal Diseases - metabolism; Retinal Diseases - prevention & control; Traumas. Diseases due to physical agents; Up-Regulation; Oxygen; Retinopathy; Cone; Rat; Rod; Rodentia; Photoreceptor; Retina; Basic fibroblast growth factor; Gene expression; Trauma; Eye; Eye disease; Vertebrata; Mammalia; Animal; Hyperoxia; Light; Hypoxia; Protection
• ISSN: 0146-0404; 1552-5783

To test whether tissue oxygen levels affect the vulnerability of photoreceptors to damage by bright continuous light (BCL).
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 (electroretinogram, ERG).
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.
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.