Labeling of red blood cells with Tc-99m after oral administration of SnCl₂ ¦ Concise communication

Abstract

In vivo labeling of red blood cells with Tc-99m was possible after prior oral administration of SnCl₂, both in rats and human volunteers. Absorption of oral SnCl₂ was low but sufficient for more than 95% labeling efficiency. Prior i.v. administration of stannous chloride is known to induce in vivo labeling of red blood cells with pertechnetate. We have observed that such labeling is possible even after oral administration of stannous chloride. Nearly 95% of the circulating radioactivity and 93.7% of the administered radioactivity was in RBCs 30 min after i.v. injection of ^99mTcO₄^- in rats that were fed 5 mg of stannous chloride (3.13 mg Sn²⁺ ion) 2 hr before injection. Red blood cells from four human volunteers could bind pertechnetate, both in vitro and in vivo, after oral administration of 100 mg of SnCl₂. We have obtained a blood-pool image of the human heart by labeling the RBCs in vivo by this method. We have also studied various parameters affecting the in vivo binding of RBCs with Tc-99m-such as the amount of orally administered SnCl₂, the time of injection of radionuclide after oral SnCl₂, and the optimum time for the imaging.