Influence of the bifunctional chelate on the biological behavior of 99mtc-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 99mTc. In vitro binding studies using isolated human granulocytes indicated specific receptor binding of the radiolabeled conjugates. The fraction of granulocyteassociated activity was determined after incubation with total blood. Biodistribution studies of the 99mTc-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.