The Stimulating Effect of the beta-Endorphin-Like Peptide Immunorphin on the Human T-Lymphoblastoid Cell Line Jurkat Is Mediated by a Non-Opioid Receptor for beta-Endorphin.

It was shown that beta-endorphin and the synthetic decapeptide SLTCLVKGFY that corresponds to the amino acid sequence 364-373 of the human IgG heavy chain (referred to as immunorphin) is able to stimulate growth of the human T-lymphoblastoid cell line Jurkat. The antagonist of opioid receptors naloxone did not inhibit the stimulating effect of the peptides. Studies on [(3)H]-immunorphin binding to Jurkat cell receptors have demonstrated that it binds with high affinity to naloxone-insensitive receptors (K(d) = 1.3 nM; n = 5.2 x 10(5)). Unlabeled beta-endorphin and the 6-10 fragment of immunorphin completely inhibited the labeled ligand specific binding to naloxone-insensitive receptors on T lymphocytes (K(i) = 1.4 x 10(-7) and 3.7 x 10(-5) M, respectively). Thus, beta-endorphin and immunorphin share the naloxone-insensitive receptors on human T-lymphoblastoid cell line Jurkat.

Beta-endorphin-like peptide SLTCLVKGFY reduces the production of 11-oxycorticosteroids by rat adrenal cortex through nonopioid beta-endorphin receptors.

Beta-endorphin-like peptide immunorphin (SLTCLVKGFY), a selective agonist of nonopioid beta-endorphin receptor, was labeled with tritium to specific activity of 24 Ci/mmol. It was used for the detection and characterization of nonopioid beta-endorphin receptors on rat adrenal cortex membranes (Kd = 31.6 +/- 0.2 nM, Bmax = 37.4 +/- 2.2 pmol/mg protein). Immunorphin at concentrations of 10(-9) to 10(-6) M was found to inhibit the adenylate cyclase activity in adrenal cortex membranes, while intramuscular injection of immunorphin at doses of 10-100 microg/kg was found to reduce the secretion of 11-oxycorticosteroids from the adrenals to the bloodstream.