Comparison of the aerobic and anaerobic reduction of oxidized glutathione in liver homogenates

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Abstract
There was no disappearance of reduced glutathione incubated aerobically with pigeon liver homogenate, but with rat liver homogenate 36% of the initial reduced glutathione disappeared in 1 hr. at 30[degree]. On incubation with boiled rat liver or pigeon liver homogenate 17% of the initial reduced glutathione disappeared in 1 hr. In homogenates of rat and guinea pig liver the anaerobic rate of reduction of oxidized glutathione was more rapid than the aerobic rate. The aerobic reduction of oxidized glutathione in the first 10 min. was followed by reoxidation of the reduced glutathione formed. In pigeon liver homogenates the initial (0-20 min.) aerobic and anaerobic rates of reduction of oxidized glutathione were approximately equal. Addition of oxidized triphosphopyridine nucleotide (final concentration up to 0.11 mM) to pigeon liver homogenates stimulated the aerobic and anaerobic rates of reduction of oxidized glutathione to the same degree. At concentrations of oxidized triphosphopyridine nucleotide above 0.11 mM the anaerobic reduction of oxidized glutathione was lower than the aerobic reduction. Citrate, fumarate and glucose 6-phos-phate stimulated oxidized glutathione reduction in pigeon liver homogenates. The addition of oxidized triphosphopyridine nucleotide (0.04 mM) further stimulated the reduction. In pigeon liver homogenates incubated under 5% carbon dioxide, 5 mM-pyruvate inhibited the anaerobic reduction of oxidized glutathione by about 50% but had no effect aerobically. Higher concentrations (25 mM) of pyruvate inhibited both the aerobic and anaerobic reduction of oxidized glutathione by about 70%. Added fumarate and oxidized triphosphopyridine nucleotide both partially counteracted the inhibition of oxidized glutathione reduction due to pyruvate. Fumarate was more effective in aerobic conditions. The significance of these findings is discussed in relation to the mechanism of maintenance of glutathione in the reduced form in intact tissue.