Methylmercury intoxication activates nitric oxide synthase in chick retinal cell culture

Abstract The visual system is a potential target for methylmercury (MeHg)intoxication. Nevertheless, there are few studies about the cellularmechanisms of toxicity induced by MeHg in retinal cells. Variousreports have indicated a critical role for nitric oxide synthase (NOS)activation in modulating MeHg neurotoxicity in cerebellar and corti-cal regions. The aim of the present study is to describe the effects ofMeHg on cell viability and NOS activation in chick retinal cellcultures. For this purpose, primary cultures were prepared from 7-day-old chick embryos: retinas were aseptically dissected and dissociatedand cells were grown at 37oC for 7-8 days. Cultures were exposed toMeHg (10 µM, 100 µM, and 1 mM) for 2, 4, and 6 h. Cell viability wasmeasured by MTT method and NOS activity by monitoring theconversion of L-[H 3 ]-arginine to L-[H 3 ]-citrulline. The incubation ofcultured retina cells with 10 and 100 µM MeHg promoted an increaseof NOS activity compared to control (P < 0.05). Maximum values (P< 0.05) were reached after 4 h of MeHg incubation: increases of 81.6± 5.3 and 91.3 ± 3.7%, respectively (data are reported as mean ± SEMfor 4 replicates). MeHg also promoted a concentration- and time-dependent decrease in cell viability, with the highest toxicity (areduction of about 80% in cell viability) being observed at theconcentration of 1 mM and after 4-6 h of incubation. The present studydemonstrates for the first time the modulation of MeHg neurotoxicityin retinal cells by the nitrergic system.