Hypoxia increases superoxide anion production from bovine coronary microvessels, but not cardiac myocytes, via increased xanthine oxidase.
OBJECTIVE
To determine if 30 min of hypoxia (PO2 8-10 Torr) affects basal, mitochondrial, or xanthine oxidase-derived lucigenin-detectable superoxide anion (O2.-) production by intact isolated bovine coronary microvessels and myocytes.


METHODS
O2.- was quantitated by lucigenin-elicited chemiluminescence. Antimycin A (10 microM) and hypoxanthine (0.1 mM) were employed to increase O2.- from mitochondria and xanthine oxidase, respectively.


RESULTS
Chemiluminescence from microvessels and myocytes was enhanced (approximately twofold, P < 0.05, n = 8-10) by inhibition of Cu,Zn-SOD via pretreatment with diethyldithiocarbamate (10 mM, 30 min) and was decreased (P < 0.05, n = 8-10) by an intracellular scavenger of O2.- (10 mM Tiron), but not by added SOD (3 microM, n = 8-10). In the presence of SOD inhibition, hypoxia produced a hypoxanthine-dependent (n = 8-10) twofold increase in chemiluminescence (P < 0.05, n = 10) in microvessels but not in myocytes. Other combinations of hypoxia, antimycin, or hypoxanthine did not significantly alter chemiluminescence.


CONCLUSIONS
Lucigenin appears to detect a basal intracellular source of O2.- in both microvessels and myocytes that is not derived from mitochondria or xanthine oxidase. Exposure to hypoxia does not appreciably increase basal O2.- in vessels or myocytes, but if exogenous hypoxanthine is supplied, microvessels show an increase in O2.- production presumably derived from xanthine oxidase.
Kaminski
P M
PM
Department of Physiology, New York Medical College, Valhalla 10595, USA.
Wolin
M S
MS
D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000166:Acridines / Q000494:pharmacology; D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D002196:Capillaries / Q000378:metabolism; D002417:Cattle; D003326:Coronary Circulation; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000494:pharmacology; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000378:metabolism*
D000166:Acridines; D007042:Hypoxanthines; D013481:Superoxides; C032456:antimycin; C033472:10,10'-dimethyl-9,9'-biacridinium; D019271:Hypoxanthine; D004958:Estradiol; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000968:Antimycin A; C073106:3,17-diacetoxyestra-1,3,5(10)-trien-2-carboxylic acid; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D010100:Oxygen