Using a Langendorff-perfused rat heart preparation and selective
electrodes, we determined
nitric oxide (NO) and
oxygen levels in cardiac tissue. An NO-selective
electrode that was calibrated by electron spin resonance (ESR) spectroscopy was inserted into the middle of the myocardium in the left ventricle. Simultaneously, we used an O2-selective
electrode to measure the partial pressure of
oxygen (pO2) in the perfusate, Krebs-Henseleit (K-H)
solution, that was ejected from the heart. After 30 min of aerobic control perfusion, hearts were subjected to 30 min of global
ischemia followed by 30 min of reperfusion. Under ischemic conditions, with a gradually decreasing pO2, NO detected by an NO-sensitive
electrode within the myocardium was gradually increased. The maximum concentration increases in NO and decreases in pO2 during global
ischemia were +10.200 +/- 1.223 microM and -58.608 +/- 4.123 mmHg, respectively. NO and pO2 levels both recovered to pre-
ischemia baseline values when perfusion was restarted after global
ischemia (reperfusion). The presence of Nomega-nitro-
L-arginine methyl ester (
L-NAME, 10 mM), a NOS inhibitor, prevented
ischemia/reperfusion-induced changes in NO. This study shows that an NO-selective
electrode that is calibrated by ESR can provide accurate, real-time monitoring of cardiac NO in normal and ischemic myocardium.