Nitric oxide increases in the retina after continuous illumination

PIEHL, L.; CAPANI, F.; FACORRO, G.B.; LOPEZ, E.M.; RUBIN DE CELIS, E.; PUSTOVRH, C.; HAGER, A.; COIRINI, H.; LOPEZ-COSTA, J.J.

BRAIN RESEARCH

Elsevier Ltd

Año: 2007 vol. 1156 p. 112 - 119

0006-8993

Continuous illumination (CI) of the retina induces an oxidative stress followed by the degeneration of photoreceptors. This phenomenon may be partially related to the excessive production of nitric oxide (NO). In order to confirm this hypothesis, the aims of this work are to determine NO levels during the illumination of the retina by electron paramagnetic resonance (EPR), and if an increase of NO is found, to characterize the NOS isoform responsible of the increment by using Western blot. Sprague Dawley rats were continuously illuminated with white light (12,000 lux) for 2, 24, 48 hours (hs), 5 and 7 days while control rats were maintained at light/dark cycles of 12/12 hs. Using EPR, an increase of NO signal was observed in the light exposed retinas peaking at 24 hs of CI. Western blot analysis showed the expression of iNOS in the illuminated retinas with a peak after 24 hs of CI, but did not show significant differences of nNOS among illuminated and control retinas. In summary, there is an increase of NO during CI which could be involved in photoreceptor degeneration.