Norepinephrine stimulates the expression of fibroblast growth factor 2 in rat brown adipocyte primary culture

To elucidate the role of norepinephrine (NE) in the hyperplasia of brown adipose tissue (BAT), we investigated the effects of NE on the expression of fibroblast growth factor-2 (FGF-2) in rat brown adipocyte primary culture and on capillary growth in an in vitro angiogenesis model in which microvascular fragments and brown adipocyte precursor cells isolated from rat BAT were grown in coculture. NE significantly increased the number of brown adipocyte precursor cells. The NE effect on cell proliferation was greatly inhibited by anti-FGF-2-specific antibody. Likewise,NE considerably increased the levels of FGF-2 mRNA and the antigen in brown adipocyte primary culture. The ability of NE to stimulate the expression of FGF-2 mRNA was blocked by actinomycin D or was inhibited partly by propranolol. Moreover, NE considerably increased the in vitro capillary growth and the level of FGF-2 antigen in the coculture. These results suggest that NE is a crucial factor to mediate FGF-2 production, in part via the beta-adrenergic receptor, in rat brown adipocytes and to stimulate the cell proliferation and capillary growth in BAT by an autocrine/paracrine mechanism.