A COMPARISON OF CONTINUOUS VERSUS INTERMITTENT LIGHT EXPOSURE ON APOPTOSIS

Citation
Sh. Li et al., A COMPARISON OF CONTINUOUS VERSUS INTERMITTENT LIGHT EXPOSURE ON APOPTOSIS, Current eye research, 15(9), 1996, pp. 914-922
Citations number
27
Categorie Soggetti
Ophthalmology
Journal title
ISSN journal
02713683
Volume
15
Issue
9
Year of publication
1996
Pages
914 - 922
Database
ISI
SICI code
0271-3683(1996)15:9<914:ACOCVI>2.0.ZU;2-O
Abstract
Purpose. We recently found that continuous light exposure at a moderat e intensity triggered apoptosis of photoreceptor cells. Since intermit tent light exposure is known to cause more severe retinal damage than is continuous light exposure, we sought to determine if intermittent l ight exposure also triggered apoptosis of photoreceptor cells. Methods . Lewis albino rats were reared, for 2 weeks, in cyclic light and dark adapted for 24 hr before light exposure. Rats were exposed to intermi ttent light or continuous light for 6 or 9 hr, respectively. Light-exp osed rats were killed by lethal injection at three timepoints: immedia tely after light exposure, after 6 hr of dark recovery following light exposure and after 24 hr of dark recovery following light exposure. R etinal damage after light exposure was evaluated by morphology, morpho metry, the terminal transferase-mediated biotin dUTP nick end labeling (TUNEL) technique for identification of nicked/cleaved nuclear DNA an d agarose gel electrophoresis of retinal DNA. Results. Evaluation of m orphology confirmed that intermittent light exposure caused more photo receptor cell damage than did continuous light exposure of the same du ration and intensity. The TUNEL technique showed that photoreceptor nu clei contained nicked or cleaved DNA after either intermittent or cont inuous light exposure, although more TUNEL-positive nuclei were observ ed after intermittent exposure. Agarose gel electrophoresis of retinal DNA showed internucleosomal DNA fragmentation, which is associated wi th apoptosis in samples from intermittent light exposure. Conclusions. These data demonstrated that intermittent light exposure triggered ap optosis in more photoreceptor cells than did continuous light exposure of the same intensity and duration.