gp91phox-containing NAD(P)H oxidase mediates attenuation of nitric oxide-dependent control of myocardial oxygen consumption by ANG II

We have previously reported that ANG II stimulation increased superoxide anion (O-2(-)) through the activation of NAD(P)H oxidase and inhibited nitric oxide (NO)-dependent control of myocardial oxygen consumption (M(V) over dot(O2)) by scavenging NO. Our objective was to investigate the role of NAD(P)H oxidase, especially the gp91(phox) subunit, in the NO-dependent control of M(V) over dot(O2). M(V) over dot(O2) in mice with defects in the expression of gp91(phox) [gp91(phox)(-/-)] was measured with a Clark-type oxygen electrode. Baseline M(V) over dot(O2) was not significantly different between wild-type (WT) and gp91(phox)(-/-) mice. Stimulation of NO production by bradykinin (BK) induced significant decreases in M(V) over dot(O2) in WT mice. BK-induced reduction in M(V) over dot(O2) was enhanced in gp91(phox)(-/-) mice. BK-induced reduction in M(V) over dot(O2) in WT mice was attenuated by 10(-8) mol/l ANG II, which was restored by coincubation with Tiron or apocynin. In contrast to WT mice, BK-induced reduction in M(V) over dot(O2) in gp91(phox)(-/-) mice was not altered by ANG II. There was a decrease in lucigenin (5 x 10(-6) mol/l)-detectable O-2(-) in gp91(phox)(-/-) mice compared with WT mice. ANG II resulted in significant increases in O-2(-) production in WT mice, which was inhibited by coincubation with Tiron or apocynin. However, ANG II had no effect on O-2(-) production in gp91(phox)(-/-) mice. Histological examination showed that the development of abscesses and/or the invasion of inflammatory cells occurred in lungs and livers but not in hearts and kidneys from gp91(phox)(-/-) mice. These results indicate that the gp91(phox) subunit of NAD(P)H oxidase mediates O-2(-) production through the activation of NAD(P)H oxidase and attenuation of NO-dependent control of M(V) over dot(O2) by ANG II.