PRESENCE OF THE BROWN FAT-SPECIFIC MITOCHONDRIAL UNCOUPLING PROTEIN AND IODOTHYRONINE 5'-DEIODINASE ACTIVITY IN SUBCUTANEOUS ADIPOSE-TISSUEOF NEONATAL LAMBS

Subcutaneous adipose tissue of neonatal lambs has been examined for th e presence of markers diagnostic of thermogenic brown fat. Uncoupling protein, uncoupling protein mRNA, and iodothyronine 5'-deiodinase acti vity were each detected in subcutaneous adipose tissue, as well as in the major internal fat depot (perirenal), of newborn lambs. These brow n fat markers were not present, however, in adipose tissue of adult sh eep. It is concluded that subcutaneous fat in newborn lambs is functio nally 'brown', and similar to the internal fat; subcutaneous and inter nal adipose tissues follow a similar developmental path - from 'brown' to 'white'.