Figure 7.

Loss of TDO activity in liver homogenates under hypoxic conditions. Determination of murine TDO ex vivo activity. Livers of WT or TDO-deficient C57BL/6 mice were homogenized in PBS and liver homogenisates were added to TDO-buffer in 48-well microtiter plates, followed by an incubation under normoxia (20% O₂) or other oxygen amounts (1–9% O₂) for 4 h at 37°C. Then the reaction was stopped using 30% trichloroacetic acid and the kynurenine amount was determined in the supernatants via supplementation of Ehrlich's reagent and absorbance at 492 nm. n = 3 independent experiments with three replicates each. A significant alteration of kynurenine levels as compared to the normoxia control is marked with asterisks (^∗∗∗∗ p ≤ 0.0001), as determined via a two-tailed, unpaired t-test. The bars indicate the mean value ± SEM.