Tissue-specific regulation of α_1B, β₁, and β₂-adrenergic receptor mRNAs by thyroid state in the rat

Steady state levels of the mRNAs for α_1B, β₁- and β₂-adrenergic receptors (α_1BAR, β₁AR, β₂AR) were quantified by DNA excess solution hybridization assays in the heart, lungs, and liver of rats. Tissues for RNA extraction were obtained from euthyroid and thyroidectomized rats and from thyroidectomized rats treated with a single dose of thyroxine. Thyroidectomy resulted in significant decreases in β₁AR and β₂AR mRNAs in heart and lung and α_1BAR mRNA in liver, whereas the levels of β₂AR mRNA in liver and α_1BAR mRNA in heart and lung were significantly increased. All these changes were reversed within 20 hours of a single s.c. injection of 1 mg/kg thyroxine. These findings indicate for the first time that thyroid state regulates mRNA levels for adrenergic receptors, and that this regulation is tissue- and receptor-specific. The changes in adrenergic receptor mRNAs correlate with and probably underlie the well documented, thyroid-dependent changes in the cellular densities and physiological reactivities of adrenergic receptors.