Role of nitric oxide and its interaction with superoxide in the control of mitochondrial respiration in isolated cardiac muscle

The present study was designed to investigate the effects and properties of nitric oxide (NO) and its interaction with superoxide anion ($O.-2$) in the modulation of cellular respiration in intact cardiac muscle. When tissue NO levels were altered after development of heart failure or following hypoxia and reoxygenation treatment, effects of these models on cardiac muscle respiration were also studied.; Tissue respiration of canine, bovine and rat cardiac muscle was acutely and dose-dependently suppressed by NO derived from the NO donor SNAP and the endogenous stimuli of endothelial NO bradykinin and the acetylcholine analog carbachol. Endogenously formed kinins were also observed to inhibit respiration via an NO mechanism in canine cardiac muscle. The respiratory inhibitory effects of NO were rapidly reversible within 15 min. NO appears to directly inhibit mitochondrial respiration, because the mitochondrial uncoupler dinitrophenol (DNP) overrode inhibition of respiration by the cGMP analog 8-bromo-cGMP, but not that by NO, and because inactivation of endogenous soluble guanylate cyclase with ODQ did not alter respiratory inhibitory actions of SNAP.; Superoxide generation from pyrogallol also acutely reduced cardiac muscle respiration, but a large portion of this inhibition remained for up to an hour. The cell-permeable $O.-2$ scavenger Tiron antagonized both acute and prolonged effects of pyrogallol on tissue respiration. Transport of extracellular $O.-2$ via anion channels on plasma membranes contributes to inhibition of respiration by this reactive species.; Peroxynitrite (ONOO−) generation from SNAP plus pyrogallol caused a greater inhibition of tissue respiration, when compared to similar doses of SNAP or pyrogallol alone. This inhibition of respiration by ONOO− was virtually irreversible for up to an hour. Both acute and prolonged effects of ONOO− on cardiac muscle respiration were largely attenuated by preventing generation of this reactive species with Tiron and by scavenging the species directly with uric acid. Intracellular formation of ONOO− appears to be the primary source of this species inhibiting respiration.; When NO biosynthesis is impaired after development of heart failure induced by rapid left ventricular pacing, stimuli of endogenous NO formation, bradykinin and carbachol, did not modulate basal or DNP-potentiated tissue respiration in failing canine cardiac muscle. However, the NO donor SNAP exerted similar inhibitory effects on basal and DNP-potentiated tissue respiration in the failing cardiac muscle, as in normal cardiac muscle.; Following hypoxia and reoxygenation treatment, cardiac muscle respiration was significantly suppressed for up to one hour. This inhibition was markedly attenuated by the NO synthase inhibitor L-NNA, Tiron and uric acid, and was potentiated by the substrate for NO biosynthesis L-arginine, SNAP, bradykinin and carbachol. This suggests that endogenous ONOO− formation from elevated NO and $O.-2$ levels during post-hypoxic reoxygenation is responsible for the observed respiratory suppression. Overproduction of $O.-2$ during post-hypoxic reoxygenation appears to be in part derived from endothelial xanthine oxidase and cyclooxygenase. This inhibition of respiration by endogenous formation of ONOO&mi...