MODULATION OF OBESE GENE-EXPRESSION IN RAT BROWN AND WHITE ADIPOSE TISSUES

The ob gene mRNA expression in rat brown adipose tissue (BAT) and epid idymal white adipose tissue (WAT) was measured on Northern blots hybri dized with a rat ob gene probe, The level of ob gene mRNA in BAT was a bout 40% of that in WAT, Fasting (36 h) or semi-starvation (10 days) d ecreased the ob gene mRNA level in both tissues by 62-68%, and cold ex posure at 6 degrees C (24 h) decreased it in BAT (-84%) but not in WAT , Acute administration of the beta(3)-adrenergic agonist Ro 16-8714 de creased the ob gene mRNA level in BAT (-51%) and WAT (-28%) of lean Zu cker rats and only in BAT (-74%) of obese falfa rats, This study demon strates that, in the rat, the ob gene is not only expressed in WAT but also in BAT, and suggests that in these two tissues, the modulation o f the ob gene expression might be more closely associated with known a lterations in cell lipid content than with changes in sympathetic acti vity.