IN-VIVO DETECTION OF NITRIC-OXIDE AND NOX SPECIES USING EX-VIVO ELECTRON-PARAMAGNETIC-RESONANCE SPECTROSCOPY

Nitric oxide is a paramagnetic molecule that exhibits high affinity fo r heme proteins, forming a mixture of nitrosylated valency hybrids tha t can be precisely characterized using low-temperature electron parama gnetic resonance spectroscopy. In red blood cells, nitric oxide will f orm paramag netic complexes with deoxyhemoglobin or be oxidized to nit rite and nitrate by oxyhemoglobin with formation of paramagnetic methe moglobin. We have developed a technique to monitor temporal changes in local nitric oxide production in vivo, by sampling arterial and venou s blood across a tissue bed and measuring changes in hemoglobin-nitric oxide and methemoglobin concentration ex vivo using electron paramagn etic resonance spectroscopy. Changes in local nitric oxide concentrati on are further clarified by quantifying plasma nitrite/nitrate levels. With these techniques, we have observed that whole body hyperthermia increases portal venous concentrations of hemoglobin-nitric oxide and organic radicals that are consistent with enhanced nitric oxide syntha se activity, cytotoxic leukocyte activity, and cellular oxidative stre ss in splanchnic tissues. (C) 1997 Academic Press.