Billy L. Byrd

Liposomal preparations of calcium- or zinc-DTPA have a high efficacy for removing colloidal ytterbium-169 from rat tissues

Results from this study demonstrate that liposomes increase the effectiveness of chelating agents in removing heavy metals from contaminated tissues in vivo. We compared the ability of free and liposomal preparations of Ca- and Zn-diethylenetriaminepentaacetic acid (DTPA) to remove 169Yb from tissues of rats previously injected intravenously with either soluble or colloidal forms of 169Yb . Although single injections of liposomal Zn-DTPA were better than the free chelator in reducing the body burden of 169Yb administered in a soluble form (citrate), the liposomal preparations of Zn-DTPA or Ca-DTPA were even more effective in removing the 169Yb that had been injected as the colloidal form. However, a second injection of liposomal Zn-DTPA given 8 days after the initial treatment was not as effective in removing 169Yb as a second injection of the free chelator. Whether injected in the free or liposomal forms, Ca-DTPA was more effective than Zn-DTPA in removing the colloidal 169Yb . Significantly lower amounts of colloidal 169Yb remained in the liver, kidney, muscle, bone, and blood of rats after injection of the liposomal preparations of Ca- or Zn-DTPA than in the corresponding organs of the controls (P less than 0.01). The liposomal preparations were also more efficient in reducing the retention of colloidal 169Yb in bone and blood than the free chelators (P less than 0.01).

Comparison of 68Ga-EDTA, [l-11C]α-aminoisobutyric acid, and [99mTC]sodium pertechnetate in an experimental blood-brain barrier lesion

Unilateral opening of the blood-brain barrier (BBB) in rats, induced by infusion of a hyperosmotic solution of mannitol into the left internal carotid artery, was applied to compare 68Ga-EDTA, [1-11C]alpha-aminoisobutyric acid (using the long-lived 14C-labeled analog), and [9mTc]sodium pertechnetate as agents for diagnosis of BBB disruption. Of the three agents and two time intervals studied, 68Ga-EDTA at 30 min postinjection gave the highest target-to-nontarget ratio. In addition, 68Ga-EDTA, unlike commonly used [99mTc]sodium pertechnetate, can be used in conjunction with positron emission tomography, which could make possible earlier and better assessment of BBB defects using 68Ga-EDTA.