ANGIOTENSIN-II IN BROWN ADIPOSE-TISSUE FROM YOUNG AND ADULT ZUCKER OBESE AND LEAN RATS

Previous studies demonstrated that interscapular brown adipose tissue (ISBAT) produces angiotensin II (ANG II), which facilitates sympathetic neurotransmission (SN). ANG II content and regulation of SN were examined in young (17 days) and adult (16 wk) Zucker obese and lean rats. ANG II content in ISBAT from preobese rats was decreased compared with lean littermates. Evoked H-3 overflow in ISBAT slices preloaded with [3H]NE was greater in preobese rats compared with control. ANG II increased evoked H-3 overflow in ISBAT slices to a greater extent in preobese rats compared with control. [H-3]NE uptake in ISBAT slices from preobese rats was decreased compared with control. In adult obese rats, plasma renin activity was decreased compared with control. ISBAT ANG II content was increased in adult obese rats compared with control. Evoked H-3 overflow in ISBAT slices preloaded with [H-3]NE was not different between obese and control. ANG II did not increase evoked H-3 overflow in obese rats; however, ANG II increased evoked H-3 overflow in lean rats. [H-3]NE uptake in ISBAT slices from obese rats was decreased compared with control. These results suggest that ANG II modulation of SN activity is decreased in ISBAT from adult obese rats. In contrast, in young obese rats, increased SN activity and ANG II regulation of SN were evident in brown adipose tissue.