Rho Activator I(Cat. # CN01) is useful for efficient activation of RhoA, RhoB, and RhoC in a variety of cultured cells.  The reagent activates Rho proteins in fibroblasts, neurons, epithelial, endothelial, and hematopoietic cells as well as other primary and immortalized lines.  Cells treated with the activator can be subjected to any one of a number of assays that indicate an increase in Rho activity, including focal adhesion or stress fiber staining (Cat. # BK005) and Rho activity assays by G-LISA™ (Cat. # BK124).  See Figure 1 for example of Rho activation measured by the G-LISA assay. There are many activators of RhoA,B and C proteins in mammalian cells. Commonly used ones are calf serum (1), lysophosphatidic acid (LPA)(1) and calpeptin (2). Through years of experience in Rho activation assay, Cytoskeleton Inc. has identified calpeptin as a compound that activates many cell types and has a long timespan of activation for ease of use so this is the active component in Rho Activator I Cat.# CN01. Note: Calpeptin is used as an inhibitor of calpain, but it also inhibits myosin light chain phosphorylation which is connected to stress fiber formation and hence possibly to RhoA activation. 

References

1. Ren, XD., Kiosses, WB., & Schwartz, MA.  Regulation of the small GTP-binding protein Rho by cell adhesion and the cytoskeleton. EMBO J. 18: 578-585 (1999).
2. Schoenwaelder, SM., & Burridge, K.  Evidence for a calpeptin-sensitive protein-tyrosine phosphatase upstream of the small GTPase Rho.  J. Biol. Chem. 274: 14359-14367 (1999)