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Inorganic nitrite (NO(2)(-)) is emerging as a regulator of physiological functions and tissue responses to ischemia, whereas the more stable nitrate anion (NO(3)(-)) is generally considered to be biologically inert. Bacteria express nitrate reductases that produce nitrite, but mammals lack these specific enzymes. Here we report on nitrate reductase activity in rodent and human tissues that results in formation of nitrite and nitric oxide (NO) and is attenuated by the xanthine oxidoreductase inhibitor allopurinol. Nitrate administration to normoxic rats resulted in elevated levels of circulating nitrite that were again attenuated by allopurinol. Similar effects of nitrate were seen in endothelial NO synthase-deficient and germ-free mice, thereby excluding vascular NO synthase activation and bacteria as the source of nitrite. Nitrate pretreatment attenuated the increase in systemic blood pressure caused by NO synthase inhibition and enhanced blood flow during post-ischemic reperfusion. Our findings suggest a role for mammalian nitrate reduction in regulation of nitrite and NO homeostasis.

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Inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, namely statins, exert pleiotropic actions beyond lipid-lowering effects. Their pharmacological activity on atherosclerotic plaque stability and vascular inflammation appears to be mediated, at least in part, by nitric oxide (NO). With the aim of enhancing the nonlipid-lowering properties of selected statins, we introduced a NO-releasing moiety into the structure of pravastatin (NCX 6550) and fluvastatin (NCX 6553). NO release was evaluated as nitrosylhemoglobin adduct formation by using EPR spectroscopy in rat blood. Both compounds produced a linear time-dependent increase in nitrosylhemoglobin formation, which is consistent with slow NO release kinetics. In PC12 cells, unlike their native statins, both compounds stimulated cGMP formation (NCX 6550, EC 50