It has previously been established that angiotensinogen mRNA is present in brown and white adipose tissue of the rat. To determine whether angiotensinogen gene expression is present in adipocytes as compared with other cell elements, we have examined angiotensinogen mRNA in 3T3-L1 cells. These cells undergo adipocyte differentiation when the culture reaches confluence. To accelerate the differentiation process, cells were treated with dexamethasone and isobutylmethylxanthine for 3 days. On the 7th day after drug treatment, RNA was extracted from cells and was examined for angiotensinogen mRNA using a full-length rat angiotensinogen cDNA. Angiotensinogen mRNA was readily detected in differentiated 3T3-L1 cells. To determine when the gene is expressed, a 7-day time course from day 0 (before drug treatment) to day 7 was examined for the presence of angiotensinogen mRNA. In addition, C2 cells, a clonal cell line that does not differentiate into adipocytes, were examined. Angiotensinogen mRNA was detected on days 2-7 after drug treatment in 3T3-L1 cells, with no detectable levels in untreated 3T3-C2 cells. When 3T3-C2 cells were subjected to the same drug regimen, angiotensinogen mRNA levels increased in the same time course as 3T3-L1 cells. However, the increase in angiotensinogen message was greater in differentiating 3T3-L1 cells than in the nondifferentiating 3T3-C2 cells. Thus angiotensinogen mRNA is present in both adipocytes and in fibroblast-like cells and appears to be regulated by steroids.