(-)[3H]amlodipine binding to rat cardiac membranes

J Cardiovasc Pharmacol. 1991 Apr;17(4):587-92. doi: 10.1097/00005344-199104000-00010.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amlodipine
  • Animals
  • Female
  • Gallopamil / pharmacology
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Isradipine
  • Kinetics
  • Membranes / metabolism
  • Myocardium / metabolism*
  • Nifedipine / analogs & derivatives*
  • Nifedipine / metabolism
  • Oxadiazoles / pharmacology
  • Rats
  • Rats, Inbred Strains
  • Stereoisomerism
  • Temperature

Substances

  • Oxadiazoles
  • Amlodipine
  • Gallopamil
  • Nifedipine
  • Isradipine