Fig. 3.

¹²⁵I-T₃(T₄)/¹³¹I-T₃(T₃) ratio is higher in cytosol of cerebral cortex (A) and skeletal muscle (B) from hypothyroid wild-type (WT) than from D2 knockout (D2KO) mice but do not differ in liver (C) and kidney (D) cytosol. Assessment of ¹²⁵I-T₃/¹³¹I-T₃ ratios in extracts of tissue cytosol from WT and D2KO mice that received ¹²⁵I-T₄ and ¹³¹I-T₃ for 24 and 4 h, respectively, prior to obtaining tissues. Observed tissue ratios were divided by the ¹²⁵I-T₃/¹³¹I-T₃ ratio in the serum of each mouse to correct for ¹²⁵I-T₃ serum contribution to intracellular T₃. Results are means ± SE of 4 animals per group. **P < 0.01, ***P < 0.001.