Effect of calmodulin antagonists on depolarization-induced MAPK activation. A, MTN cultures were pretreated for 3 hr with 25 μg/ml of W12 (K12) or 25 μg/ml W13 (K13) or left untreated (N.S. and KCl). Then, cultures were stimulated for 5 min with high potassium (K12, K13, and KCl) or were left unstimulated (N.S.). Protein extracts were analyzed on Western blot with an anti-Ptyr antibody (top panel). Membranes were stripped and reprobed with an anti-pan-ERK monoclonal antibody (bottom panel). B, MTN cultures were pretreated for 3 hr with 5 μg/ml W13 (K13) or left untreated (N.S. and KCl). Then, cultures were stimulated for 5 (5′) or 15 (15′) min with high potassium (KCl andK13) or were left unstimulated (N.S.). Protein extracts were analyzed on Western blot with an anti-Ptyr antibody (top panel). Membranes were stripped and reprobed with the anti-pan-ERK antibody (bottom panel). ERK2-labeled arrows indicate the position of ERK2 protein in A andB.