Simultaneous measurement of NO• and PO2 from tissue by in vivo EPR

We describe a technique that utilizes electron paramagnetic resonance (EPR) to measure NO . and pO(2) directly, and non-invasively, from tissue in vivo. Diethyldithiocarbamate (DETC) was injected with iron so as to complex with NO . in the tissue. Glory tan oxygen-sensitive, paramagnetic material) was also implanted into the tissue of interest (brain or liver). Because the signals arising from glory and NO-Fe-(DETC)(2) did not overlap, they could be monitored and measured simultaneously in vivo. The glory was not responsive to NO . and/or DETC. As model systems we either injected SNP tan NO . donor) into animals and monitored NO . and pO(2) simultaneously from brain, or endotoxin (lipopolysaccharide; LPS) was injected in order to induce a septic episode and NO . and pO(2) measured from liver. We found a close correlation between levels of SNP-derived NO . and brain pO(2) in vivo. During sepsis, liver pO(2) decreased dramatically at 300-360 min after endotoxin injection, and this coincided with decreases in mean arterial blood pressure and increased tissue NO . detected. These studies demonstrate the potential usefulness of this technique for making direct in vivo measurements of NO . and pO(2) simultaneously from tissue. (C) 1999 Academic Press.