[125I]azido-DTLET as a tool for selective covalent labeling of delta-opioid receptors in rat brain sections.
The binding kinetics and pharmacological selectivity of the photoaffinity delta-opioid ligand [125I]azido-DTLET (Tyr-D-Thr-Gly-Phe(pN3)-Leu-Thr) were investigated in serial frozen sections from rat neostriatum prior to ultraviolet irradiation (i.e., in conditions of reversibility). Scatchard analysis of saturation binding experiments indicated that [125I]azido-DTLET binds to both a high (KD = 5.04 nM) and a low (KD = 38 nM) affinity site. Binding to the low-affinity site was no longer detectable in the presence of unlabeled [D-Ala2,N-MePhe4,Gly-Ol5]enkephalin (DAGO), suggesting that this site corresponds to mu-opioid receptors. This interpretation was further supported by the dose-dependent inhibition of the binding of [3H]DAGO by non-radioactive azido-DTLET. Binding to the high-affinity site was totally inhibited, in a dose-dependent fashion, by a variety of opioid drugs among which delta-opioid ligands showed the highest order of potency. It is concluded that, in the nanomolar range, [125I]azido-DTLET constitutes a highly selective tool for covalent labeling of delta-opioid receptors in rat brain sections.
Pasquini
F
F
Montreal Neurological Institute, McGill University, Quebec, Canada.
Jomary
C
C
Garbay-Jaureguiberry
C
C
Roques
B P
BP
Beaudet
A
A
D000345:Affinity Labels / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001386:Azides / Q000378:metabolism*; D001667:Binding, Competitive; D003342:Corpus Striatum / Q000378:metabolism*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017465:Receptors, Opioid, delta / Q000378:metabolism*
D000345:Affinity Labels; D001386:Azides; D004745:Enkephalins; D007457:Iodine Radioisotopes; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C044210:tyrosyl-threonyl-glycyl-(4-azidophenylalanyl)-leucyl-threonine