Glutathione Measurements
The amounts of reduced (GSH) and oxidized glutathione (GSSG) in the heart and liver tissues were determined from the extent of 5′-dithiobis(2-nitrobenzoic acid) (DTNB) reduction for GSH and from NADPH consumption in the presence of glutathione reductase for GSSG [41]. Briefly, 30 mg of the frozen tissue was mixed with 300 μlof1% meta-phosphoric acid. After 15 min on ice, the samples were centrifuged at 10,000 g for 15 min, and the supernatants used for analyses.
Glutamate Cysteine Ligase (GCL) Activity
Activities of GCL in the heart and liver tissues were determined according to a published procedure [42].