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Comparative binding properties of linear and cyclic δ‐selective enkephalin analogues: [ 3 H]‐[D‐Thr 2 , Leu 5 ] enkephalyl‐Thr 6 and [ 3 H]‐[D‐Pen 2 , D‐Pen 5 ] enkephalin
Author(s) -
Delay-Goyet Philippe,
Zajac Jean-Marie,
Rigaudy Pascal,
Foucaud Bernard,
Roques Bernard P.
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)80827-9
Subject(s) - selectivity , enkephalin , chemistry , stereochemistry , receptor , crystallography , biochemistry , opioid , catalysis
The range of δ‐selectivity of linear and cyclic analogues of enkephalin in rat brain was found to be: [D‐P n 5 ] enkephalin (DPLPE) > [D‐P n 5 ] enkephalin (DPDPE) > [D‐Thr 2 , Leu 5 ] enkephalyl‐Thr 6 (DTLET) > [D‐Ser 2 , Leu 5 ] enkephalyl‐Thr 6 (DSLET). Saturation experiments performed with [ 3 H]DPDPE and [ 3 H]DTLET in NG108‐15 cells and rat brain showed similar binding capacities for both the ligands, but the δ‐affinity of [ 3 H]DTLET ( K D ≈ 1.2 nM) was much better than that of [ 3 H]DPDPE ( K D ≈ 7.2 nM). The rather low δ‐affinity of DPDPE induced high experimental errors cancelling the benefit of its better δ‐selectivity. Binding experiments in rat or guinea‐pig brains showed, in both cases, the better δ‐selectivity of [ 3 h]dtlet compared to [ 3 h]slet. The former peptide remains at this time the most appropriate radioactive probe for binding studies of δ‐receptor.