Fig. 8.

Relaxation of coronary artery to nitroglycerin is attenuated by PDBu-evoked superoxide generation. A: nitroglycerin relaxed coronary arterial rings precontracted with KCl (30 mM) and PDBu (10 μM) in a dose-dependent manner (n = 20–25). The relaxation of coronary artery to nitroglycerin is significantly shifted to the right in arterial rings precontracted with PDBu compared with KCl, and this inhibition in relaxation is prevented by tiron (10 mM), a superoxide scavenger. B and C: in contrast, relaxation to 8-bromo-cGMP (B; n = 5–8) and forskolin (C; n = 5–8) is not affected by tiron. D: a model showing potential mechanisms involved in the induction of coronary artery contraction by the PKC activator PDBu through a Src kinase activation of Nox-2-derived hydrogen peroxide generation and inhibition of nitroglycerin-induced relaxation by Nox-2-derived superoxide.