Fig. 2. Rhythmic transcription profiles and protein expression of core clock genes in Rat-1 cells. (A) Rat-1 fibroblasts that were stably transfected with different reporter constructs (Bmal1::Luc, Per2::Luc and Rev-erb::Luc) were synchronized by treatment with 200 nM dexamethasone (Dex) for 1 hour. Cells were then switched to recording medium and bioluminescence (photon counts per minute) was recorded using photon-multiplier tubes. (B) Phase relationships with respect to synchronization were depicted after the data were de-trended by 24 hour moving average. (C) Damped oscillation of Bmal1::Luc Rat-1 cells (synchronized by 50% horse serum) can be re-initiated by medium change, treatment with Dex, or a combination of both. As expected, Dex treatment induced a phase-delay compared with medium-change alone. Arrow shows the time of addition of Dex and/or medium change. (D) Representative western blot (WB) of REV-ERB in Rat-1 cells synchronized by 200 nM Dex and harvested at 4-hour intervals. The time points indicated are relevant to the time of Dex treatment. This experiment was repeated three times.