In vivo ESR measurement of free radicals in whole mice

The in vivo measurement of nitroxide radicals in whole mouse was carried out by L-band ESR spectroscopy. Spectra were successively observed in hepatic and bladder domains of female mice after intravenous administration of spin-labeled compounds (CPROXYL or TEMPOL). The signal intensities from both domains decreased gradually. The kinetic constants of clearance in the hepatic domain were 0.09/min for CPROXYL and 0.71/min for TEMPOL. The clearance constants in the bladder domain coincided with those in the hepatic domain within experimental error, whereas the constants in collected blood were 1/7-1/10 of those in the hepatic or bladder domains. The mechanism of clearance of nitroxide radicals in whole mice is discussed.