Effect of phorbol 12-myristate 13 acetate (PMA, 1 nM) on the total outflow of reduced cytochrome c (a); normalised acetylcholine (ACh) response (b); NADPH oxidase activity (c); xanthine oxidoreductase activity (XOR) (d); phosphorylation of Ser345-p47phox (e), p38 (f) and ERK1/2 (g) in guinea-pig hearts. PMA was given either alone or in combination with (from left to right): 4 μM chelerythrine (Chele), 100 μM 5HD, 3 μM glibenclamide (Glib), 5 μM TTFA, 1 mM apocynin (Apo), 250 μM allopurinol (Allo), and 150 IU/mL SOD. Values are means ± SEM of at least five experiments in a–d and of four experiments in e–g. # p < 0.05 vs. control; * p < 0.05 vs. PMA.