COMPONENTS OF THE RENIN-ANGIOTENSIN SYSTEM IN ADIPOSE-TISSUE - CHANGES WITH MATURATION AND ADIPOSE MASS ENLARGEMENT

White adipose tissue is a rich source of angiotensinogen protein and m RNA. Studies in clonal cells suggest that angiotensinogen, and its cle avage product, angiotensin II, are involved in preadipocyte differenti ation into mature fat cells. No studies have determined whether angiot ensinogen is also involved in adipose tissue development in vivo. In t his report, we studied male Wistar rats at two stages of development t o determine if angiotensinogen protein and mRNA are increased in retro peritoneal fat depots of rapidly growing young, lean, 8-week-old rats compared to 26-week-old rats that are fatter, but are undergoing less rapid adipose tissue growth. We also assessed renin mRNA and angiotens in 1-generating activity, since it is less clear whether renin is loca lly produced in adipose tissue. We found that angiotensin 1-generating activity was measurable in adipose tissue and adipocytes, but renin m RNA teas undetectable by Northern blot analysis. Angiotensinogen mRNA was abundant in adipocytes, but was absent in stromal-vascular cells o f adipose tissue. Angiotensinogen content per 10 million fat cells was similar to-threefold higher in 8-week-old rats compared to 26-week-ol d rats (p <.0002). Angiotensinogen mRNA was similar to twofold higher in adipocytes of 8-week-old rats compared to 26-week-old rats. The age -related decline in angiotensinogen protein and mRNA indicates that th e local renin-angiotensin system may play an important role in adipose tissue growth, and possibly contribute to the changes in adipose mass and cellularity seen in old and senescent rats.