[Effect of nitrites and nitrates on bovine retina in vitro]

Uveitis is an endocular inflammation that forms one of the most serious manifestations of Behçet disease. Nitric oxide (NO) is a molecule that expresses important immunoinflammatory properties and is produced by NO synthases (NOS). In previous studies, we showed an elevated production of endogenous NO during Behçet's and idiopathic uveitis. These results led us to investigate the effect of nitrites (NO2-) and nitrates (NO3-) (physiologically stable metabolites of NO) on fragments of bovine retina in order to determine the role of nitric oxide (NO) in the genesis of retinal lesions during uveitis.

Retinas were removed from freshly enucleated bovine eyes and cultured in DMEM, 10% CFS in presence of nitrites (NaNO2) or nitrates (NaNO3) at different concentrations. The cultures were processed at 37 degrees C, 5% CO2 in a humidified chamber. Cultured retinas were observed by inverse microscopy and then fixed in formaldehyde. Histological studies were conducted after H & E staining.

Cultured retina showed alterations when exposed to concentrations of nitrites and nitrates higher than 200 microM and 250 microM, respectively. These alterations were dose-dependent and affected the cellular and tissular structures. Morphological and histological studies suggested that the toxic effect is apoptotic and/or necrotic for both effectors.

Our investigations showed that nitrites and nitrates, two physiologically stable metabolites of NO, have a deleterious effect on cultured retina. NO, produced in inflammatory processes during uveitis may be implicated in the genesis of the retinal lesions observed during the exacerbation phase of the disease.