Premium
Characterization of K Opioid Receptors in Neurosecretosomes from Bovine Posterior Pituitary
Author(s) -
Pesce Guido,
Lang Michael A.,
Russell James T.,
Rodbard David,
Gainer Harold
Publication year - 1987
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.1471-4159.1987.tb02882.x
Subject(s) - etorphine , enkephalin , binding site , receptor , chemistry , stereochemistry , opioid , endocrinology , medicine , biology , biochemistry , (+) naloxone
The binding properties of opioid receptors on isolated nerve terminals (neurosecretosomes) from bovine posterior pituitaries were characterized. Both [ 3 H]etorphine and [ 3 H]ethylketocyclazocine ([ 3 H]EKC) showed high‐affinity binding with complex binding isotherms, consistent with the presence of multiple classes of binding sites. [D‐Ala 2 ,D‐Leu 5 ]enkephalin showed no specific binding and failed to displace [ 3 H]etorphine at high concentrations, indicating the absence of μ, δ, or benzomorphan ( K 2 ) sites. Mathematical modelling of the data suggested the presence of three classes of binding sites. The first was of high affinity with K d values of 0.9 and 2.0 nM for etorphine and EKC, respectively. The second class of sites appeared to bindetorphine with a K D of 150 n M , and EKC with extremely low affinity (unmeasurable binding). The third class of sites was characterized by K D values of 7 and 2 μ M for etorphine and EKC, respectively. These results indicate that the nerve terminals of bovine posterior pituitary contain opioid binding sites of the K type. Futhermore, these binding sites appear heterogeneous, consisting of at least two and possibly more subtypes or states.