title: Interaction of the synthetic peptide octarphin with rat adrenal cortex membranes.
abstract: The synthetic peptide octarphin (TPLVTLFK, fragment 12-19 of β-endorphin), a selective agonist of the non-opioid β-endorphin receptor, was labeled with tritium yielding specific activity of 28 Ci/mmol. The binding of [3H]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.
authors.affiliation: Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, pr. Nauki 6, 142290 Pushchino, Moscow Region, Russia.
authors.forename: Y N
authors.initials: YN
authors.lastname: Nekrasova
authors.forename: Y A
authors.initials: YA
authors.lastname: Zolotarev
authors.forename: E V
authors.initials: EV
authors.lastname: Navolotskaya
mesh_terms: D000302:Adrenal Cortex / Q000166:cytology*; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D003080:Cold Temperature; D018869:Heat-Shock Response; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009842:Oligopeptides; C555005:octarphin