Acute exposure of mature mouse adipocytes to ATRA induces UCP1 expression. ATRA (1 μM) was supplemented at day 8. Total RNA and protein were harvested after 24 h and analyzed by RT-qPCR and immunoblotting, respectively. Relative mRNA expression levels of FABP4, UCP1 and RARβ were determined by normalization to levels of TBP. (A) 3T3-L1. (B) WT MEFs. (C) C3H10T½. (D) Rb−/− MEFs. (E) Protein levels of UCP1 with GAPDH used as a loading control. (A-D) Data represents mean + SEM (n = 3). *, p < 0.05 versus vehicle-treated cells at day 9.