Influence of the bifunctional chelate on the biological behavior of (99m)Tc-labeled chemotactic peptide conjugates.

Conjugates of For-MLFK and For-NleLFNleYK with S-benzyl mercaptoacetyl dipeptides containing, respectively, zero, one, and two carboxyl functions in their structures were prepared and labeled with (99m)Tc. In vitro binding studies using isolated human granulocytes indicated specific receptor binding of the radiolabeled conjugates. The fraction of granulocyte-associated activity was determined after incubation with total blood. Biodistribution studies of the (99m)Tc-peptides in normal mice revealed a very fast blood clearance proceeding mainly via the hepatobiliary system. Urinary excretion was higher for conjugates containing carboxyl functions in their ligand structures.