Evaluation of ^99mTc Labeled Amino Acids as Radiopharmaceuticals IV. S-Substituted Cysteines and N-Substituted Iminodiacetic Acids

Abstract

Sixteen ^99mTc labeled ligands were evaluated as scintigraphic agents. The ligands studied were cysteine, glutathione, their S-substituted derivatives, lysine-N^∈ N^∈-diacetic acid, glycylglycine-N, N-diacetic acid, glycylglycylglycine-N, N-diacetic acid, taurine-N, N-diacetic acid, hydrazine-N, N-diacetic acid, ethylenediamine-N, N-diacetic acid, and propylene-l, 3-diamine-N¹-, N¹-diacetic acid. The ligands were labeled with ^99mTc by the SnCl₂ method with more than 95% yield. The in vivo behavior of the ^99mTc labeled ligands were studied in golden hamsters and dogs. The organ distribution in golden hamsters indicated clearance both by hepatobiliary and renal systems. The pancreas/blood ratios were much lower in the ^99mTc ligands than in ⁷⁵Se-selenomethionine. Scintigraphic studies in dogs showed that the liver and kidneys were well visualized but the accumulation by the pancreas was not sufficient for clear visualization.