Transfer of nitric oxide from the liver to erythrocytes — An ESR study using nitroglycerin-treated mice

Nitric oxide (NO) formation in the liver and blood of the mouse following intraperitoneal treatment with nitroglycerin (glycerol trinitrate, GTN) was determined using electron spin resonance (ESR) spectroscopy. ESR signals of heme-NO complexes were detected at maximum levels within 5 min in the liver, but increased to a maximum level about 15–30 min later in the blood. GTN is not metabolized to release NO in vitro in the blood of the mouse. The hepatic microsomes which showed the heme-NO complexes ESR signals were incubated with mouse erythrocytes, with the result that a hemoglobin-NO signal was obtained from the erythrocytes. The activities of microsomal cytochrome P-450, the hepatic level of glutathione, and the reduction rate of nitroxide radicals in the in vivo liver, measured using L-band ESR spectroscopy, were temporarily decreased following GTN administration. In conclusion, NO in the liver could be scavenged by circulating erythrocytes, which might minimize NO-induced liver damage.