Growth hormone-releasing factor and fibroblast growth factor regulate somatostatin gene expression.

A multiple peptide-synthesizing clonal rat cell line was used to study the effect(s) of GRF and basic fibroblast growth factor (bFGF) on the synthesis and secretion of somatostatin (SS). The presence of SS-specific mRNA in 44-2C cells was shown morphologically by in situ hybridization. The release and cellular content of SS increased significantly after treatment with rat hypothalamic GRF (rGRF), the ED50 for rGRF stimulation of intracellular SS was 1.9 X 10(-11) M. GRF stimulated SS production in serum-supplemented and serum-free cultures. Results obtained after incubation of 44-2C cells with 125I-labeled rGRF indicated uptake and nuclear localization of rGRF by 44-2C cells. FGF stimulated the secretion and cellular content of SS. We propose that bFGF regulates the short term secretion and accumulation of SS and mediates rGRF-stimulated SS expression.