Localization of Radiolabeled Chemotactic Peptide at Focal Sites of Escherichia coli Infection in Rabbits: Evidence for a Receptor-Specific Mechanism

The infection imaging properties of a high-affinity ""Tc-labeled chemotactic peptide receptor agonist (N-formyl-methionyl-leucyl-phenylalanine-lysine; N-For-MLFK) were compared with a low-affinity agonist (N-Acetyl-MLFK; N-Ac-MLFK), a moderate-affinity antagonist (N-isobutyloxycarbonyl-MLFK; N-iBoc-MLFK) and non specific inflammation imaging agents. Methods: All peptides were prepared by solid-phase methods and purified by high-perfor mance liquid chromatography. The products were assayed in vitro for N-formyl-methionyl-leucyl-phenylalanine receptor binding and Superoxide production. Three types of studies were performed in rabbits with Escherichia coli infection: (Study A) Four groups of six animals were coinjected with "Tc-N-For-MLFK-hydrazinonicoti-namide (N-For-MLFK-HYNIC) plus 111ln-immunoglobulin G, 111In-red blood cells or1111n-diethylene triamine pentaacetic acid. (Study B) Three groups of six rabbits were coinjected with 1111n-leukocyte