TRIIODOTHYRONINE REGULATES BETA-3-ADRENOCEPTOR EXPRESSION IN 3T3-F442A DIFFERENTIATING ADIPOCYTES

The effect of thyroid hormones on the beta 3-adrenoceptor expression w as studied in the preadipose 3T3-F442A cell line. As assessed by molec ular and pharmacological analyses, triiodothyronine addition to differ entiating 3T3-F442A cells caused a 2.3-fold increase in beta 3-adrenoc eptor mRNA levels, which was correlated with a parallel induction of b eta 3-adrenoceptor number and of beta 3-adrenoceptor coupling to the a denylate cyclase system. Nuclear transcription experiments showed that triiodothyronine did not significantly alter the transcription rate o f the beta 3-adrenoceptor gene. By contrast, the hormone increased by 36% the half-life of beta 3-adrenoceptor mRNA. Triiodothyronine exhibi ted a discrete effect on beta 3-adrenoceptor expression when added to mature 3T3-F442A adipocytes. This study indicates that thyroid hormone s exert a differentiation-dependent and post-transcriptional regulatio n of beta 3-adrenoceptor expression in adipocytes.