Ligand binding profiles of delta-opioid receptor in human cerebral cortex membranes: evidence of delta-opioid receptor heterogeneity.
In this study, receptor binding profiles of opioid ligands for subtypes of opioid delta-receptors were examined employing [3H]D-Pen2,D-Pen5-enkephalin ([3H]DPDPE) and [3H]Ile(5,6)-deltorphin II ([3H]Ile-Delt II) in human cerebral cortex membranes. [3H]DPDPE, a representative ligand for delta1 sites, labeled a single population of binding sites with apparent affinity constant (Kd) of 2.72 +/- 0.21 nM and maximal binding capacity (Bmax) value of 20.78 +/- 3.13 fmol/mg protein. Homologous competition curve of [3H]Ile-Delt II, a representative ligand for delta2 sites, was best fit by the one-site model (Kd = 0.82 +/- 0.07 nM). Bmax value (43.65 +/- 2.41 fmol/mg) for [3H]Ile-Delt II was significantly greater than that for [3H]DPDPE. DPDPE, [D-Ala2,D-Leu5]enkephalin (DADLE) and 7-benzylidenaltrexone (BNTX) were more potent in competing for the binding sites of [3H]DPDPE than for those of [3H]Ile-Delt II. On the other hand, deltorphin II (Delt II), [D-Ser2,Leu5,Thr6]enkephalin (DSLET), naltriben (NTB) and naltrindole (NTI) were found to be equipotent in competing for [3H]DPDPE and [3H]Ile-Delt II binding sites. These results indicate that both subtypes of opioid delta-receptors, delta1 and delta2, exist in human cerebral cortex with different ligand binding profiles.
Dept. of Pharmacology, Chonbuk University Medical School, Chonju Chonbuk, Republic of Korea. keewon@moak.chonbuk.ac.kr
K W
KW
Kim
S J
SJ
Kim
B S
BS
Shin
H Y
HY
Choi
D000328:Adult; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000378:metabolism*; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000378:metabolism; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008297:Male; D008566:Membranes / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D017465:Receptors, Opioid, delta / Q000378:metabolism*
D008024:Ligands; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; C088242:deltorphin II, Ile(5,6)-; D020881:Enkephalin, D-Penicillamine (2,5)-