Sensitive fluorometric assays for glutathione peroxidase and reductase

A microfluorometric adaptation of the method of D. E. Paglia and W. N. Valentine has been made which can assay glutathione peroxidase activity in less than 100 μg of tissue. As in the original method, the oxidized glutathione produced in the reaction is coupled to the oxidation of NADPH by glutathione reductase. No inhibition by NADPH was found. A similar method can be used to measure glutathione reductase. These methods have been used to assay glutathione peroxidase and reductase in rat brain and in a neuronal and a glial cell line using samples containing 15 μg of protein. The assays are sensitive enough to allow multiple determinations of the enzymes in brain regions, organotypic tissue cultures, and microwell cell cultures.