DECREASED NOREPINEPHRINE TURNOVER RATE IN THE BROWN ADIPOSE-TISSUE OFPREOBESE FA FA ZUCKER RATS/

Norepinephrine (NE) content and turnover rate, and the activity of dop amine-beta-hydroxylase (DBH) were measured in the brown adipose tissue (BAT) of developing Zucker rats of the three genotypes: Fa/Fa and Fa/ fa (with a lean phenotype) and fa/fa (phenotypically obese). As early as 15 days of age, namely at a pre-obese stage, BAT NE content and tur nover rate are already reduced in fa/fa rats,just like they are at 50 days. The development of DBH activity is completely impaired in fa/fa rats. These results demonstrate that the reduction in sympathetic tone in BAT of fa/fa rats is already present before the onset of phenotypi c obesity.