Fig. 5. Effect of cold exposure and hormonal [triodothyronine (T₃) or thyroxine (FT₄)] treatment on liver response to oxidative challenge in vitro. Tissue susceptibility to stress was evaluated by determining the variations, with concentration of homogenates, of light emission from a luminescent reaction. Emission values are given a percentages of an arbitrary standard (44 ng ml^–1 peroxidase). The curves were computed from experimental data using equation E=a C/exp(b C). Preparations from control (C; solid line), 10-day cold exposed (CE; dotted line), T₃-treated (HT₃; broken line), and T₄-treated (HT₄; broken line) rats.