RADIOLABELED FMLP IS A VALUABLE PEPTIDE FOR DIAGNOSTIC IMAGING
Fatemeh Keshavarzi and Parviz Ashtri
Department of biology, sanandaj branch, Islamic Azad University, Iran
Objective: Molecular imaging techniques are increasingly being used in the localization of disease, the staging of disease and for therapy control. This attributed to the favorable pharmacokinetics and specific tumor targeting characteristics, together with the overexpression of their receptors on the tumor cells, making these peptides attractive agents for imaging and therapy. Because of the importance of labeled peptides, the development and optimization of methodologies for the labeling of peptides with 18F and 123I is a very important goal. The chemotactic peptide N-formyl-Met-Leu-Phe is a bacterial product that binds to polymorph nuclear leukocytes and mononuclear macrophages, possibly via cell membrane receptors. Binding of this peptide or of many synthetic analogues initiates’ leukocyte chemo taxis.
Material & Methods: Labelling studies were done both by direct method using chloramine-T according to Khawli(1989) and indirect method using [125I and 131I]SIB according to Zalutsky (1987). Then, biodistribution studies were performed both in normal mice and the ones bearing 50 μl turpentine for 24h, promoted inflammation in right leg. Furthermore, the ability of the labelled peptide conjugate to bind to human polymorph nuclear leukocytes (PMN) was determined using in vitro assays.
Results and Discussion: With increasing in pH, yield of labeled FMLF decreased perhaps because of interaction OH to carboxyl group of SIB. The maximum activity was observed in the right leg which injected with turpentine due to infection and increase in blood circulation. Also, this peptide was conjugated to PMN specifically and maximum activity was 66%. Biological studies of labelled FMLF show a low uptake of thyroid but a high uptake at urine and bladder. Perhaps because of FMLF molecular weight is low in comparison to other peptides and for this reason this molecule could pass from blood to urine.