Abstract
In vivo targeting of urokinase by magnetic force was examined in mice, Urokinase was labeled with 125I and was further conjugated with magnetite through a polyethylene glycol derivative. The magnetic urokinase was injected into the tip part of a tail vein of a mouse, while magnetic force (0∼12000 G) was applied to the root part of the tail as a target site. The distribution of radioactivity among various parts of a mouse was measured after the animal was sacrificed. By magnetic force of 12000 G, approximately as much as 60% of magnetic urokinase injected were localized in the target, the tail root. By applying magnetic force of 12000 G to the heart, approximately 20% of magnetic urokinase injected were attracted in the heart. There was almost no retention of magnetic urokinase in the tail root when the magnetic force of 12000 G was applied even 10 sec after the injection of the magnetic urokinase. It seems that if the magnetic urokinase misses the chance to be attracted by magnetic force and passes through the lung and the liver, it is readily trapped there. It is possible that magnetic urokinase might be used for targeting in the future.
