Properties of a superoxide anion-generating microsomal NADH oxidoreductase, a potential pulmonary artery PO2 sensor
Mohazzab, K.M.; Wolin, M.S.
American Journal of Physiology 267(6 Pt 1): L823-L831
1994
ISSN/ISBN: 0002-9513 PMID: 7810686 Document Number: 428704
In this study, we describe properties of a microsomal NADH oxidoreductase that is a potential PO-2-dependent source of vasoactive reactive O-2 species in the calf pulmonary artery. Microsomes show an NADH-dependent production of superoxide anion (O-2- cntdot ), as detected by lucigenin-elicited chemiluminescence, a superoxide dismutase inhibited reduction of nitro blue tetrazolium (NBT) and 2,6-dichlorophenol-indophenol, and O-2 consumption. The microsomal production of O-2- cntdot was modulated by physiologically relevant levels of NADH and PO-2, and O-2- cntdot 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 apprx 558 nm was observed. Arterial O-2- cntdot levels (chemiluminescence) were also reduced by NBT and microsomal electron transport inhibitors. In pulmonary arteries, NBT selectively inhibited PO-2 and lactate elicited changes in force generation, presumably by trapping O-2- cntdot and preventing H-2O-2 formation. Thus these studies are consistent with an involvement of O-2- cntdot -derived H-2O-2 generation via a microsomal NADH-cytochrome b-558 electron transport system in calf pulmonary artery smooth muscle PO-2 and lactate-elicited tone responses.