Fig. 9.

TPA and growth factors regulated neuregulin expression by cultured astrocytes. Cells incubated in DMEM containing low serum (1%) received DMSO as a control (lane 1) or several growth factors (EGF, lane 2; bFGF, lane 3; PDGF, lane 4) and TPA (lane 5). The concentrations of these stimuli were: bFGF, 10 ng/ml; EGF, 10 ng/ml; PDGF, 10 ng/ml; and TPA, 30 nm. After 24 hr of incubation, cell lysates and culture media were analyzed separately for neuregulin using an immunoblotting technique. Ashows a Western blot of cell lysates, and B shows that of culture media. The small arrowheads inA show neuregulin-immunopositive bands with apparent molecular sizes of 65, 60, and 52 kDa, respectively. The positions of molecular mass markers (in kilodaltons) are shown to theleft of each panel.