Elucidation and Characteristics of Non-opioid beta-Endorphin Receptors in Rat Adrenal Cortex

E. V. Navolotskaya^1*, Yu. A. Kovalitskaya¹, Yu. A. Zolotarev², N. Yu. Kudryashova³, E. N. Goncharenko³, A. A. Kolobov⁴, E. A. Kampe-Nemm⁴, N. V. Malkova¹, V. V. Yurovsky⁵, and V. M. Lipkin¹

¹Branch of Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, pr. Nauki 6, Pushchino 142290, Moscow Region, Russia; fax: (7-0967) 33-0527; E-mail: navolots@fibkh.serpukhov.su

²Institute of Molecular Genetics, Russian Academy of Sciences, pl. Kurchatova 2, Moscow 123182, Russia; fax: (7-095) 196-0221

³Faculty of Biology, Lomonosov Moscow State University, Moscow 117899, Russia; fax: (7-095) 147-3897

⁴State Research Center for Institute of Highly Pure Biopreparations, Ministry of Health of the Russian Federation, Pudozhskaya ul. 7, St. Petersburg 197110, Russia; fax: (7-812) 235-5504

⁵Department of Medicine, University of Maryland School of Medicine, 10 S. Pine St., Baltimore, MD 21201, USA; fax: (1-410) 706-0321

^* To whom correspondence should be addressed.

Received September 24, 2003; Revision received November 4, 2003

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beta-Endorphin-like decapeptide immunorphin (SLTCLVKGFY), a selective agonist of non-opioid beta-endorphin receptor, was labeled with tritium to specific activity of 24 Ci/mmol. It was used for the detection and characterization of non-opioid beta-endorphin receptors on rat adrenal cortex membranes (K_d1 = 39.6 ± 2.0 nM, B_max1 = 40.7 ± 2.3 pmol/mg protein; K_d2 = 0.25 ± 0.01 µM, B_max2 = 187.8 ± 9.4 pmol/mg protein). beta-Endorphin was found to inhibit the [³H]immunorphin specific binding to membranes (K_i = 70.0 ± 9.2 nM); naloxone, [Met⁵]enkephalin, and alpha- and gamma-endorphins tested in parallel were inactive. Immunorphin at concentrations of 10^-9-10^-6 M was found to inhibit the adenylate cyclase activity in adrenocortical membranes, while intramuscular injection of immunorphin at doses of 10-100 µg/kg was found to reduce the secretion of 11-oxycorticosteroids from the adrenals to the bloodstream.

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KEY WORDS: beta-endorphin, naloxone, peptides, receptors, adrenal cortex

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