Interaction of the synthetic peptide octarphin with rat adrenal cortex membranes

• Published in: Biochemistry (Moscow) Vol. 77; no. 12; pp. 1377 - 1381
• Main Authors: Nekrasova, Y. N., Zolotarev, Y. A., Navolotskaya, E. V.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.12.2012; Springer; Springer Nature B.V
• Subjects: Adrenal Cortex - cytology; Adrenal glands; Amino Acid Sequence; Animals; Beta-endorphin; Biochemistry; Biomedical and Life Sciences; Biomedicine; Bioorganic Chemistry; Cell Membrane - metabolism; Cold Temperature; Heat-Shock Response; Intermedin; Life Sciences; Membranes; Microbiology; Oligopeptides - chemical synthesis; Oligopeptides - chemistry; Oligopeptides - metabolism; Peptides; Protein Binding; Rats; Rats, Wistar; Rodents; Tritium; naloxone; peptides; β-endorphin; receptors; adrenal cortex
• ISSN: 0006-2979; 1608-3040
• DOI: 10.1134/S000629791212005X

The synthetic peptide octarphin (TPLVTLFK, fragment 12–19 of β-endorphin), a selective agonist of the nonopioid β-endorphin receptor, was labeled with tritium yielding specific activity of 28 Ci/mmol. The binding of [ 3 H]octarphin to rat adrenal cortex membranes was studied under normal conditions as well as after cold and heat shocks. It was found that under normal conditions [ 3 H]octarphin specifically binds to the membranes with high affinity: K d1 = 36.3 ± 2.5 nM, B max1 = 41.0 ± 3.8 pmol/mg protein. The specific binding of [ 3 H]octarphin to the membranes was inhibited by unlabeled β-endorphin ( K i = 33.9 ± 3.6 nM) and the agonist of the non-opioid receptor decapeptide immunorphin ( K i = 36.8 ± 3.3 nM). Unlabeled naloxone, [Leu 5 ]- and [Met 5 ]enkephalins, α- and γ-endorphins, and corticotropin were inactive ( K i > 1 μM). Both cold and heat shocks decreased the binding affinity: K d2 = 55.6 ± 4.2 nM and K d3 = 122.7 ± 5.6 nM, respectively. In both cases, the maximal binding capacity of the receptor did not change. Thus, even a short-term thermal shock significantly affects the sensitivity of the non-opioid β-endorphin receptor of adrenal cortex membranes.