Figure 2.

(A) Bar graph shows Ucp1 mRNA levels in the retroperitoneal fat pad from parental A/J, B6, F1 hybrid, and RI strains of mice derived from the parental mice. Mice were housed at 5°C in groups of two to three mice per pen for 7 days before the isolation of RNA. Induction in the cold is similar to that caused by a β3-adrenergic agonist. Data are presented as the mean ± SE. The number of animals (n) of each strain and the results of statistical analyses by ANOVA (Fisher’s PLSD test in Statview 4.1) are given in the lower chart. Strains sharing asterisks in a row are not significantly different from each other at P = 0.05. (B) UCP1 immunohistology of paraffin-embedded sections from interscapular brown fat (iBAT) and retroperitoneal fat (wBAT) from A × B8 and A × B15 mice demonstrates the organization of brown adipocytes into clusters that resemble fields of densely packed brown adipocytes characteristic of iBAT. The size of these regions in wBAT may be quite variable, depending upon the strength of the induction.