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Interaction of Opiates with Opioid Binding Sites in the Bovine Adrenal Medulla: I. Interaction with δ and μ Sites
Author(s) -
Castanas E.,
Bourhim N.,
Giraud P.,
Boudouresque F.,
Cantau P.,
Oliver C.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb04046.x
Subject(s) - dadle , etorphine , chemistry , adrenal medulla , enkephalin , binding site , opioid peptide , biochemistry , stereochemistry , opioid , receptor , biology , endocrinology , catecholamine , (+) naloxone
In the present study we examined the interaction of opiates with the δ and μ opioid binding sites in the bovine adrenal medulla. [ 3 H][D‐Ala 2 , D‐Leu 5 ]‐enkephalin ([ 3 H]DADLE) in the presence of saturating concentrations of morphiceptin was used to analyze δ site interactions, whereas either [ 3 H]DADLE in the presence of saturating concentrations of [D‐Ser 2 , Leu 5 ]‐enkephalinThr 6 (DSLET) or [ 3 H][D‐Ala 2 , Me‐Phe 4 , Gly 5 ‐ol]‐enkephalin ([ 3 H]DAGO) was used for the determination of μ sites. Both binding sites were found to interact stereo selectively with opiates. The binding was affected differentially by proteolytic enzymes (trypsin, α‐chymotrypsin, pepsin), N ‐ethylmaleimide, and A 2 ‐phospholipase. Kinetic and equilibrium binding studies revealed that in each case radiolabeled opiates interact with one class of binding sites, following simple second‐order bi molecular kinetics. Competition for binding by opiates and opioid peptides confirmed the δ and μ selectivity of these sites. Monovalent (Na + , Li + , K + ) and divalent (Mg 2+ , Mn 2+ , Ca 2+ ) ions interacted differentially with these two binding sites: In general, monovalent cations affected preferentially the apparent number of binding sites, whereas divalent ions modified the equilibrium dissociation constant. Furthermore, positive or negative cooperativity and an apparent heterogeneity of binding sites were detected under some ionic conditions.