FIG. 12.

Dio1 (type 1 deiodinase) is a representative T₃-responsive gene in the liver. Northern blot analysis showing Dio1 mRNA levels in response to normal diet (ND), hypothyroid (LID, low-iodine diet and antithyroid agents), and hyperthyroid (0.5 T₃) conditions. Dio1, upper panel, and control glyceraldehyde-3-phosphate dehyrogenase (G3pdh), lower panel. In WT mice (+/+), Dio1 mRNA is suppressed by hypothyroid conditions and induced by hyperthyroid conditions. Induction is defective in Thrb-deleted mice (−/−). Treatments: ND, normal diet; LID, hypothyroid groups (0.05% methimazole [MMI] and 1% potassium perchlorate in drinking water and low iodine chow, for 4 weeks); 0.5 T₃, hyperthyroid groups (same as LID but with T₃ added to drinking water at concentration of 0.5 mg/mL for an additional 8 days or more). Quantitation: Dio1 mRNA level in each condition is noted numerically below each lane relative to the level in +/+ mice on normal diet (assigned a value=1.0). Dio1 value is normalized to control G3pdh signal; UD, undetectable Dio1. Signals were quantified by phophorimager analysis of major bands.