Properties of a superoxide anion-generating microsomal NADH oxidoreductase, a potential pulmonary artery PO2 sensor.
In this study, we describe properties of a microsomal NADH oxidoreductase that is a potential PO2-dependent source of vasoactive reactive O2 species in the calf pulmonary artery. Microsomes show an NADH-dependent production of superoxide anion (O2-.), as detected by lucigenin-elicited chemiluminescence, a superoxide dismutase inhibited reduction of nitro blue tetrazolium (NBT) and 2,6-dichlorophenol-indophenol, and O2 consumption. The microsomal production of O2-. was modulated by physiologically relevant levels of NADH and PO2, and O2-. production was reduced by inhibitors of NADH-dependent microsomal electron transport. Microsomes catalyzed an NADH-mediated reduction of several electron acceptor dyes, cytochrome c (rotenone insensitive) and methemoglobin. On reduction with dithionite, a cytochrome with an absorbance at approximately 558 nm was observed. Arterial O2-. levels (chemiluminescence) were also reduced by NBT and microsomal electron transport inhibitors. In pulmonary arteries, NBT selectively inhibited PO2 and lactate elicited changes in force generation, presumably by trapping O2-. and preventing H2O2 formation. Thus these studies are consistent with an involvement of O2-.-derived H2O2 generation via a microsomal NADH-cytochrome b558 electron transport system in calf pulmonary artery smooth muscle PO2 and lactate-elicited tone responses.
Mohazzab
K M
KM
Department of Physiology, New York Medical College, Valhalla 10595.
Wolin
M S
MS
D000818:Animals; D002417:Cattle; D003573:Cytochrome b Group / Q000502:physiology*; D004579:Electron Transport; D016166:Free Radical Scavengers; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology*; D009243:NAD / Q000502:physiology*; D019255:NADPH Oxidases; D009580:Nitroblue Tetrazolium / Q000378:metabolism; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D011651:Pulmonary Artery / Q000378:metabolism* / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*; D014661:Vasoconstriction
D003573:Cytochrome b Group; D016166:Free Radical Scavengers; D005609:Free Radicals; D009243:NAD; D013481:Superoxides; D009580:Nitroblue Tetrazolium; C036888:cytochrome b558; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D010100:Oxygen