A. CRF affects actin cytoskeleton. MCF7 cells were plated in chamber-slides, stimulated with 10-8 M CRF or vehicle (control) for 1, 3 and 6 hours and stained with rhodamine-phalloidine. Fluorescence was measured by confocal microscopy. Results are representative of three independent experiments.B. CRF induces actin polymerization. MCF7 cells were stimulated with CRF (10-8 M) or vehicle (control) for 3 and 6 hours. Cells were harvested and the two fractions, soluble and insoluble, containing the monomeric (globular) and the polymerized (filamentous) actin respectively were isolated and analyzed by western blotting using antibody against actin. The relative proportion of F- and G-actin was determined by the concentration of monomeric (G) and total (F+G) actin and the result is presented as the G/(F+G) ratio induced by CRF compared to control; p < 0,01. Results represent the average of five independent experiments.