ESR DEMONSTRATION OF NITRIC-OXIDE PRODUCTION FROM NITROGLYCERIN AND SODIUM-NITRITE IN THE BLOOD OF RATS

Electron spin resonance (ESR) spectra of iron-metal complexes formed b y the reaction between nitric oxide ((NO)-N-.) and hemoglobin (Hb), re ferred to as nitrosylhemoglobin (HE-NO), were observed in rat blood tr eated in vitro and in vivo with nitroglycerin (GTN) at 77K. The same t ypes of spectra were also detected in rats treated with sodium nitrite (NaNO2). Two types of Hb-NO, which were identified by ESR parameters of g values and superhyperfine coupling constants (shfcc), were the 6- and 5-coordinated complexes. These two types of Hb-NO were generated in a dose-dependent manner in the blood after intraperitoneal administ ration of 1.5-6 mg of GTN. At the higher dose of GTN (6 mg), the 6-coo rdinated complex was the major species generated initially, but within 10 min, the 5-coordinated complex increased time-dependently. Quantit ative analysis of Hb-NO revealed that when GTN 0.3 mg and 0.6 mg was a dministered sublingually in rats, the concentration of Hb-NO observed in rat blood was 30% higher than the estimated concentration of GTN. T he methemoglobin and peroxide complex of hemoglobin were observed in t he blood incubated with GTN at 37 degrees C. These results suggest tha t the function of GTN was related to oxidative stress with the generat ion of W-NO. Therefore, monitoring of Hb-NO levels may be useful as an indicator of the function of various vasodilators.