Fig. 4. Effect of inhibitors of the sodium exchangers, amiloride (Am), HOE642 and ouabain (Ou), on the alkalosis-induced phosphorylation of p38-MAPK. (A) 50 µg of protein from hearts perfused under alkaline extracellular conditions (pH 8.5, 2 min) in the presence or absence of 100 µmol l^–1 amiloride, 5 µmol l^–1 HOE642 and 100 µmol l^–1 ouabain was immunoblotted against phospho-p38-MAPK (top) and total p38-MAPK (bottom) using the corresponding antibodies. (B) Densitometric analysis of phospho-p38-MAPK by laser scanning. Co, control. (C) Relation of the net p38-MAPK phosphorylation induced by each inhibitor in the presence of extracellular alkalosis to the alkalosis-induced p38-MAPK phosphorylation. Values are means ± s.e.m. for three independent experiments. *P<0.05, **P<0.01 vs control value.