Comparison of MAP kinase activation in suspended and attached cells. Exponentially growing CCL39 cells were trypsinized, resuspended in serum-containing medium, and either placed in suspension (left), as described in MATERIALS AND METHODS, or replated in tissue culture dishes (right) for the indicated times. Immunoblot analysis of the active phosphorylated form of MAP kinase was performed on total cell lysates. p-p42, phospho-p42; p-p44, phospho-p44.