The glutathione content of retinal Müller (glial) cells: the effects of aging and of application of free-radical scavengers.
The dependence of intracellular glutathione (GSH), an important radical scavenger, on aging with or without externally applied Ginkgo biloba extract EGb 761, another established radical scavenger, was studied in guinea pig M¿ller (retinal glial) cells by using the fluorescent dye monochlorobimane. The GSH content of freshly dissociated cells from untreated aged animals was significantly lower than that of young controls; most of this reduction was prevented by application of EGb 761. Culturing the cells in amino-acid-free caused a loss of up to 50% of the initial GSH content. When the culture medium contained 100 microM glutamate and 100 microM cystine, ongoing GSH synthesis counteracted the loss of GSH. The rates of net GSH synthesis were equal for the two groups of aged animals but significantly higher for cells from young controls. It is concluded that externally applied radical scavengers may enhance the protective glutathione 'reserve' of M¿ller cells in cases of neuronal degeneration.