FIGURE 2.

Rosiglitazone does not favor growth of brown over white adipocytes. Primary cultures of white adipocytes originating from UCP1-wild-type mice (C57Bl/6) and brown adipocytes originating from UCP1-KO mice (on C57Bl/6 background) were grown for 7 days separately or in co-culture in the indicated ratios, in the absence (left panel) or presence of 1 μm rosiglitazone (right panel). Where indicated, 1 μm norepinephrine (NE) had been added 2 h before harvest. Note that, in these rosiglitazone-treated white adipocytes cultures (originating from C57Bl/6 mice), the UCP1 transcripts were detected only after NE stimulation. Representative Northern blots are shown (three additional experiments gave principally the same results). Total RNA (10 μg) was used per lane, and the blot was hybridized with the UCP1 and 18 S rRNA probes. Arrows indicate wild-type (WT) and knockout (KO) UCP1 transcripts. Since rosiglitazone in UCP1-KO cells induces a transcript that co-migrates with the predominant UCP1-WT transcript, the genetic identity of the cells was verified by reverse transcription-PCR (supplemental Fig. 4). An example of a corresponding experiment where the origins of the cells (from wild-type or UCP1-KO mice) were reversed can be seen in supplemental Fig. 3.