Liver homogenate was mixed with trichloroacetic acid (TCA) to a final concentration of 5% TCA, and the mixture was incubated at 4°C for 30 min to extract GSH. The TCA extracts (10 μl) were added to 200 μl of methanol containing 1 mg/ml o-phthalaldehyde and were then incubated for 15 min at 37°C in the dark (18). Fluorescence was measured at 350/420 nm (excitation/emission). The concentration of GSH was determined from a GSH standard curve.
