title: (-)[3H]amlodipine binding to rat cardiac membranes.
abstract: Amlodipine is a newly developed long-acting dihydropyridine-based calcium antagonist. To characterize the binding properties of this compound, saturation binding studies were undertaken, using (-)[3H]amlodipine and rat cardiac membrane fragments. (-)[3H]Amlodipine bound to a single population of high-affinity binding sites with a KD of 1.68 +/- 0.12 nM, a Bmax of 0.34 +/- 0.08 pmol/mg protein, and a Hill coefficient approaching unity. Binding required up to 5 h to reach asymptote, and was pH- and temperature-sensitive. The specific binding was totally inhibited by (-) amlodipine and (-) D600 (IC50 values of 9.20 +/- 5.56 and 6.58 +/- 6.57 nM, respectively) and only partially inhibited by (+) PN 200-110, (-) Bay K 8644, (+) D600, and d-cis diltiazem (IC50 values of 60 +/- 10, 160 +/- 20, 250 +/- 40, and 200 +/- 30 nM, respectively). These results indicate that in addition to its ability to bind to the dihydropyridine and benzothiazepine recognition sites in rat cardiac membrane fragments, (-)[3H]amlodipine also binds strongly to the recognition sites for the phenylalkylamine-based calcium antagonists. The results also show that the inhibition of (-)[3H]amlodipine binding by D600 is stereospecific with (-) greater than (+)D600. Dissociation of bound (-)[3H]amlodipine was slowed under acidotic (pH 6.0) and accelerated under alkalotic (pH 10.0) conditions.
authors.affiliation: Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Vic, Australia.
authors.forename: W G
authors.initials: WG
authors.lastname: Nayler
authors.forename: X H
authors.initials: XH
authors.lastname: Gu
mesh_terms: D017311:Amlodipine; D000818:Animals; D005260:Female; D005711:Gallopamil / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D017275:Isradipine; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000378:metabolism; D010069:Oxadiazoles / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D010069:Oxadiazoles; D017311:Amlodipine; D005711:Gallopamil; D009543:Nifedipine; D017275:Isradipine