Fig. 3. Insulin and PDGF promote morphologically distinct actin structures. (A) Serum-deprived L6 GLUT4myc myoblasts were stimulated with either insulin or PDGF-BB for the times indicated in B, after which cells were fixed and stained for actin. Collapsed xy projections were obtained by confocal microscopy to reveal distinct filamentous actin structures such as stress fibers and long ruffles (a, arrows and asterisk, respectively), short ruffles (b, open arrowheads), and filopodia (c, closed arrowheads). (B) Images were obtained from three independent experiments and the presence of long and short actin ruffles was scored in at least 60 cells per condition. The means±s.e.m. are given of the proportion of cells exhibiting either of the two types of actin structure at each time point after insulin or PDGF stimulation. *, P<0.001 against time 0. (C) GLUT4myc proteins were stained with anti-Myc antibody followed by FITC-conjugated secondary antibody. Composite images of F-actin labeled with rhodamine-conjugated phalloidin and GLUT4myc protein staining are presented in cells that exhibit long ruffles (a), short ruffles (b) and filopodia (c); yellow indicates regions of co-localization. The images shown are representative of five individual experiments. Scale bar, 10 µm.