Triiodothyronine Regulates β3‐Adrenoceptor Expression in 3T3‐F442A Differentiating Adipocytes

The effect of thyroid hormones on the beta 3-adrenoceptor expression was studied in the preadipose 3T3-F442A cell line. As assessed by molecular and pharmacological analyses, triiodothyronine addition to differentiating 3T3-F442A cells caused a 2.3-fold increase in beta 3-adrenoceptor mRNA levels, which was correlated with a parallel induction of beta 3-adrenoceptor number and of beta 3-adrenoceptor coupling to the adenylate cyclase system. Nuclear transcription experiments showed that triiodothyronine did not significantly alter the transcription rate of the beta 3-adrenoceptor gene. By contrast, the hormone increased by 36% the half-life of beta 3-adrenoceptor mRNA. Triiodothyronine exhibited a discrete effect on beta 3-adrenoceptor expression when added to mature 3T3-F442A adipocytes. This study indicates that thyroid hormones exert a differentiation-dependent and post-transcriptional regulation of beta 3-adrenoceptor expression in adipocytes.