Characterization of the binding of a novel radioligand to CCKB/gastrin receptors in membranes from rat cerebral cortex.
1. We have investigated the binding of a novel radiolabelled CCKB/gastrin receptor ligand, [3H]-JB93182 (5[[[(1S)-[[(3,5-dicarboxyphenyl)amino]carbonyl]-2-phenylethyla mino]-carbonyl]-6-[[(1-adamantylmethyl) amino]carbonyl]-indole), to sites in rat cortex membranes. 2. The [3H]-JB93182 was 97% radiochemically pure as assessed by reverse-phase HPLC (RP-HPLC) and was not degraded by incubation (150 min) with rat cortex membranes. 3. Saturation analysis indicated that [3H]-JB93182 labelled a homogeneous population of receptors in rat cortex membranes (pKD=9.48+/-0.08, Bmax=3.61+/-0.65 pmol g(-1) tissue, nH=0.97+/-0.02, n=5). The pKD was not significantly different when estimated by association-dissociation analysis (pKD=9.73+/-0.11; n=10). 4. In competition studies, the low affinity of the CCKA receptor antagonists, L-364,718; SR27897 and 2-NAP, suggest that, under the assay conditions employed, [3H]-JB93182 (0.3 nM) does not label CCKA receptors in the rat cortex. 5. The affinity estimates obtained for reference CCKB/gastrin receptor antagonists were indistinguishable from one of the affinity values obtained when a two site model was used to interpret [125I]-BH-CCK8S competition curves obtained in the same tissue (Harper et al., 1999). 6. This study provides further evidence for the existence of two CCKB/gastrin sites in rat cortex. [3H]-JB93182 appears to label selectively sites previously designated as gastrin-G1 and therefore it may be a useful compound for the further discrimination and characterization of these putative receptor subtypes.
Harper
E A
EA
James Black Foundation, Dulwich, London, England.
Shankley
N P
NP
Black
J W
JW
D000818:Animals; D001569:Benzodiazepines / Q000378:metabolism / Q000494:pharmacology; D001570:Benzodiazepinones / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D001952:Bridged-Ring Compounds / Q000378:metabolism / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006727:Hormone Antagonists / Q000494:pharmacology; D007211:Indoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D008566:Membranes / Q000187:drug effects / Q000378:metabolism*; D018697:Nootropic Agents / Q000494:pharmacology; D010418:Pentagastrin / Q000494:pharmacology; D010671:Phenylurea Compounds / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012844:Sincalide / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D014316:Tritium
C090019:8-sulfocholecystokinin octapeptide; D001570:Benzodiazepinones; D001952:Bridged-Ring Compounds; D004151:Dipeptides; D006727:Hormone Antagonists; D007211:Indoles; C109753:JB93182; D018697:Nootropic Agents; D010671:Phenylurea Compounds; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin; D014316:Tritium; D001569:Benzodiazepines; C065599:PD 134308; C087260:YM 022; C080765:PD 140376; C058121:L 365260; D008536:Meglumine; D010418:Pentagastrin; D012844:Sincalide