Inverse distribution of uncoupling proteins expression and oxidative capacity in mature adipocytes and stromal-vascular fractions of rat white and brown adipose tissues

To investigate relationships between the uncoupling protein (UCP) family an d oxidative metabolism in fat pads, we measured the cytochrome oxidase acti vity, used as an index of oxidative capacity, and the mRNA content encoding UCP1, UCP2 and UCP3, Most oxidative potential was found in the stromal-vas cular fraction (SVF) of brown fat and in mature adipocytes of white fat (in guinal and periovarian). Considering the whole fat pads, the oxidative pote ntial observed in mature white adipocytes fraction was not negligible compa red with that of brown adipocytes fraction, UCP1 and UCP3 were expressed ex clusively in mature brown adipocytes. Whatever the deposit, UCP2 mRNA was m ainly localized in the SVF, These results indicate that, in fat, high oxida tive potential is not necessarily linked to high UCPs transcripts content a nd point out the oxidative capacity of SVF from brown fat, (C) 1999 Federat ion of European Biochemical Societies.