Binding of endomorphin-2 to mu-opioid receptors in experimental mouse mammary adenocarcinoma.

Abstract

Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) binds with high affinity and selectivity to the mu-opioid receptor. In the present study, [125I]endomorphin-2 has been used to characterize mu-opioid-binding sites on transplantable mouse mammary adenocarcinoma cells. Cold saturation experiments performed with [125I]endomorphin-2 (1 nM) show biphasic binding curves in Scatchard coordinates. One component represents high affinity and low capacity (K(d) = 18.79 +/- 1.13 nM, B(max) = 635 +/- 24 fmol/mg protein) and the other shows low affinity and higher capacity (K(d) = 7.67 +/- 0.81 microM, B(max) = 157 +/- 13 pmol/mg protein) binding sites. The rank order of agonists competing for the [125I]endomorphin-2 binding site was [d-1-Nal3]morphiceptin > endomorphin-2 >> [d-Phe3]morphiceptin > morphiceptin > [d-1-Nal3]endomorphin-2, indicating binding of these peptides to mu-opioid receptors. The uptake of 131I-labeled peptides administered intraperitoneally to tumor-bearing mice was also investigated. The highest accumulation in the tumor was observed for [d-1-Nal3)morphiceptin, which reached the value of 8.19 +/- 1.14% dose/g tissue.

• Authors: J Fichna, J-C do-Rego, M Mirowski, J Costentin, A Janecka
• Journal: The journal of peptide research : official journal of the American Peptide Society (J Pept Res) Vol. 65 Issue 4 Pg. 459-64 (Apr 2005) ISSN: 1397-002X [Print] Denmark
• PMID: 15813894 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Iodine Radioisotopes
• Oligopeptides
• Receptors, Opioid, mu
• endomorphin 2

Topics

• Adenocarcinoma (metabolism)
• Animals
• Binding, Competitive
• Cell Membrane (metabolism)
• Female
• Iodine Radioisotopes (metabolism)
• Mammary Neoplasms, Experimental (metabolism)
• Mice
• Mice, Inbred C3H
• Oligopeptides (metabolism)
• Receptors, Opioid, mu (metabolism)