Redox control of oxygen sensing in the rabbit ductus arteriosus.
How the ductus arteriosus (DA) closes at birth remains unclear. Inhibition of O2-sensitive K+ channels may initiate the closure but the sensor mechanism is unknown. We hypothesized that changes in endogenous H2O2 could act as this sensor. Using chemiluminescence measurements with luminol (50 [mu]M) or lucigenin (5 [mu]M) we showed significantly higher levels of reactive O2 species in normoxic, compared to hypoxic DA. This increase in chemiluminescence was completely reversed by catalase (1200 U ml-1). Prolonged normoxia caused a significant decrease in K+ current density and depolarization of membrane potential in single fetal DA smooth muscle cells. Removal of endogenous H2O2 with intracellular catalase (200 U ml-1) increased normoxic whole-cell K+ currents (IK) and hyperpolarized membrane potential while intracellular H2O2 (100 nM) and extracellular t-butyl H2O2 (100 [mu]M) decreased IK and depolarized membrane potential. More rapid metabolism of O2- with superoxide dismutase (100 U ml-1) had no significant effect on normoxic K+ currents. N-Mercaptopropionylglycine (NMPG), duroquinone and dithiothreitol all dilated normoxic-constricted DA rings, while the oxidizing agent 5,5'-dithiobis-(2-nitrobenzoic acid) constricted hypoxia-dilated rings. NMPG also increased IK. We conclude that increased H2O2 levels, associated with a cytosolic redox shift at birth, signal K+ channel inhibition and DA constriction.
Reeve
H L
HL
Department of Medicine, University of Minnesota, MN 55455, USA.
Tolarova
S
S
Nelson
D P
DP
Archer
S
S
Weir
E K
EK
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D004229:Dithiothreitol / Q000031:analogs & derivatives / Q000494:pharmacology; D004373:Ductus Arteriosus / Q000502:physiology*; D004579:Electron Transport / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D000975:Antioxidants; D016227:Benzoquinones; D015221:Potassium Channels; D013439:Sulfhydryl Reagents; C085285:dithiothreitol tetraacetate; D004228:Dithionitrobenzoic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D011188:Potassium; D010100:Oxygen; D004229:Dithiothreitol; C034257:duroquinone