FIG. 2.

Cold activation of p38 MAPK is necessary for UCP1 expression in IBAT. As described in Materials and Methods, mice were treated with two doses of the p38 MAPK inhibitor SB203580 (+SB) or vehicle solution (−SB) at 16 and 1 h before the cold exposure. IBAT was harvested from each animal to measure the levels of p38 MAPK activity and UCP1 mRNA. (A) p38 MAPK activity measured by in vitro phosphorylation of the p38 MAPK specific substrate, the ATF-2 fragment, by IBAT lysates. Levels of p38 MAPK in the tissue lysates were measured by immunoblotting with antibodies against p38 MAPK. (B) UCP1 mRNA detected by Northern blotting. The level of 18S RNA was detected with methylene blue in the blot. All results are from one of four independent experiments.