A new 99mtc labeled peptide: 99mtc β -casomorphin 6, biodistribution and imaging studies on rats

Abstract

Peptide radiopharmaceuticals have an increasing significance in nuclear medicine practice. β-casomorphin is a digestive peptide with 6 amino acids (Tyr-Pro-Phe-Pro-Gly-Pro). N terminal amino acid chain mainly tyr-pro-phe-pro structured exogen opioid peptid type beta cosomorphin are μ-receptor agonistic activity with priority. Animal studies show that β-casomorphins can act as opioid receptor agonists. The aim of this study was to label β-casomorphin with 99m Tc and to examine its usefulness as an opioid receptor binding radiopharmaceutical in Albino Wistar rats and cancer cells. β-casomorphin was labeled with 99m Tc radionuclide using bifunctional chelating agent. Quality control studies were done by Instant Thin layer chromatography (ITLC) and High performance liquid chromatography (HPLC) methods. Binding efficiency of the compound was more than 99%. It was observed as stable for at least 3 h at room temperature. Lipophilicity was also performed for labeled molecule. Imaging studies for 99m Tc labeled molecule was done in rats by using gamma camera. For biodistribution studies; 99m Tc labeled molecule was injected to the rats from tail vein and radioactivity per gr weight of each organ was measured as count per second (cps). Receptor specificity was evaluated in imaging and biodistribution studies in experimental animals. Cell labeling studies were also performed on breast and ovarien cancer cells. In terms of evaluating the biodistribution of 99m Tc-β-casomorphin molecule in rats, uterus and ovary displayed high involvement. It was also confirmed by cell labeling studies. If the radiopharmaceutical is radiolabeled with therapeutic radionuclides it would be useful for therapy for uterus, ovary and breast tumors.

Keywords

• β-casomorphin
• cancer cell
• peptide
• 99mtc
• receptor