Abstract
Abstract: :
Purpose: Protein nitration is seen in retinal light damage. Nitric oxide, the endogenous precursor molecule for protein nitration is generated by the nitric oxide synthases. To better understand the role of nitric oxide and protein nitration in light induced retinal damage we determined expression of nitric oxide synthases (NOS) upon light treatment. Methods: Albino Sprague–Dawley rats were reared in dim cyclic light. At day 60 rats were exposed to green light (1,200–1,400 lux; 490–580 nm) for different time periods (0, 0.5, 2, 4, and 8 hours) starting at 1:00 a.m. and sacrificed under dim red light. Another three groups of animals were maintained in darkness for different time periods (4, 8, or 24hours) after 8 hours of light treatment. Four animals were used in each group. Retinal proteins were extracted with Laemmli buffer and the relative levels of nitrated proteins,neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS) were determined by western analysis. Results: Several nitrotyrosine immunoreactive bands were present in the western blot and the extent of nitration appeared to increase up to a maximum of 1.6 fold during the light exposure. The level of iNOS and nNOS appeared to increase while the level of eNOS appeared to be unchanged. nNOS increased up to two fold with increasing duration of light exposure and then appeared to slowly decrease with increasing time in darkness following light exposure. iNOS followed a similar pattern but the duration of decrease in darkness was longer and the extent of decrease was less. Conclusions: There is an increase in retinal protein nitration upon intense light exposure. This increase appears to be mediated by increased levels of nNOS and iNOS in the retina.
Keywords: retina • nitric oxide • radiation damage: light/UV