Fig. 7. Effect of N17 Ras expression on LTD₄- and EGF-induced Erk-1/2 activation. The cells were cotransfected with a vector expressing dominant-negative N17 Ras along with an empty EGFP vector and then stimulated with LTD₄ (80 nM for 1 minute), EGF (100 ng/ml for 5 minutes) or not at all. The cells were then fixed, permeabilised and stained for phospho-Erk-1/2 as described in the Materials and Methods. The top three panels show from the left to the right: EGFP expression, phospho-Erk-1/2 staining and an overlay image of non-stimulated control cells. The middle three panels and the bottom three panels show the same analysis from cells stimulated with LTD₄ and EGF, respectively. The results illustrated are representative of three separate experiments.