Lately, we have directed our efforts to investigate the systematic in vivo pharmacokinetics, i.e.; the course of metabolism and distribution, of a paramagnetic nitroxide spin probe in mice. Using spectroscopy and living mice, we have monitored the in vivo reduction of a nitroxide free radical injected in a mouse vein.
Our preliminary real-time in vivo results show that the accumulation of the free radical after administration of the nitroxide was rapid, reaching a maximum value at ~ 45 min after injection, followed by a steady decrease. The decrease in the tail blood signal intensity is due to bioreduction of the nitroxide radicals by reducing agents such as ascorbic acid, glutathione, and other thiol groups.