Effect of ODQ or zaprinast on activation of the p42/p44 MAPK pathway and induction of p21waf1/cip1 by SNAP, DETA/NO, or DFMO in RASMC. ODQ (10 μM) or zaprinast (30 μM) was added to cells at the same time as the test agents. Whole-cell lysates of RASMC treated for 24 h with 30 μM SNAP, 100 μM DETA/NO, or 300 μM DFMO were then subjected to Western blot analysis for p21waf1/cip1 or phosphorylated p42/p44, as described in Materials and Methods. Control represents RASMC grown in the absence of added test agents. Data are representative of three separate experiments.