Spatiotemporal ESR-CT study on the metabolism of spin-labeled polysaccharide in a mouse

A spatiotemporal ESR-CT study, rapid three dimensional ESR imaging by which distribution and metabolism of radicals in a small region in a living body can be followed, was carried out by intravenously administering spin-labeled polysaccharides to mice. The in vivo lifetime of spin-labeled hydroxyethylstarch (TEMPO-HES) was shorter than that of spin-labeled dextran (TEMPO-DX), suggesting that the clearance of their spins depended on the stability of the polymer chains to the hydrolysis. Spatiotemporal image at the kidney domain of a mouse showed that low molecular weight TEMPO-DX was excreted into the kidney and then was transferred to the bladder. Time dependence of the ESR intensity of TEMPO-HES at certain points in the liver domain had a maximum showing that TEMPO-HES was taken into the liver and then was decomposed there by the metabolism, but the rate of decrease in the intensity was different in each part in the liver because of the difference in metabolic function. The rate of decrease of TEMPO-DX in the blood was slowed by the prior administration of dextran, meaning that the intake of TEMPO-DX into the liver from the blood was suppressed by the dextran.