Long-term effects of light damage on the retina of albino and pigmented rats.
OBJECTIVE
To observe the morphology and physiology of the retina in rats 11 weeks after a constant (24-hour) but moderate (500-lux) illumination for 1 week.


METHODS
Levels of aspartate, gamma-aminobutyric acid (GABA), glutamate, glutamine, and taurine were measured by high-pressure liquid chromatography (HPLC) in the retina and vitreous humor of albino (Wistar) and pigmented (Long-Evans) rats. Semithin sections were used to determine retinal morphology. The TUNEL method was used to detect cells degenerating by apoptosis. Because the GABAergic system has been shown to be particularly sensitive to the loss of photoreceptors, an additional immunohistochemical study using anti-GABA, anti-glutamate decarboxylase (GAD)(67) and anti-GAD(65) antibodies was performed.


RESULTS
No apparent morphologic changes were found in the retina of pigmented rats after constant illumination, whereas in albino rats disappearance of photoreceptors (except in the extreme retinal periphery) and cell bodies was observed. A significant number of TUNEL-positive nuclei also occurred in the remaining nuclear and ganglion cell layers. However, no change in the distribution of GABA, GAD(67), and GAD(65) immunoreactivities was found in either strain under constant illumination compared with control animals. Constant illumination affected the retinal levels of aspartate, glutamate, glutamine, glycine in both strains, whereas GABA contents did not change and taurine was decreased only in albino rats. A significant increase of vitreal glutamate levels was also found in both strains and of taurine levels only in albino rats.


CONCLUSIONS
Phototoxicity can provoke durable retinal alterations beyond the period of lighting, suggesting progressive and probably continuous modifications of retinal physiology, even in pigmented animals in which the retina seems morphologically normal.
Wasowicz
Marguerite
M
L'Institut National de la Santé et de la Recherche Médicale U 450, Laboratoire de Neuro-Cytologie Oculaire, 15 rue de l'Ecole de Médecine, 75006 Paris, France.
Morice
Cécile
C
Ferrari
Patricia
P
Callebert
Jacques
J
Versaux-Botteri
Claudine
C
D000818:Animals; D017209:Apoptosis; D001224:Aspartic Acid / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D008027:Light / Q000009:adverse effects*; D008137:Longitudinal Studies; D008297:Male; D011833:Radiation Injuries, Experimental / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D012160:Retina / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D013654:Taurine / Q000378:metabolism; D014822:Vitreous Body / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D005973:Glutamine; D013654:Taurine; D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid