title: The force-frequency relationship is dependent on Ca(2+)-influx via L-type- and SR-Ca(2+)-channels in human heart.
abstract: The present study investigated the influence of Bay K 8644 and nifedipine (Nif) on the force-frequency relationship and on tetanic tension and force of contraction of failing human myocardium (PAP, n = 12). In addition, ryanodine (Rya) was studied on the force-frequency relationship. Bay K 8644 (0.1 microM) increased, but Nif (0.01 microM) reduced isometric force of contraction significantly. However, both, Bay K 8644 (2 Hz vs. 0.5 Hz:
  
  
  METHODS
  -31.6 +/- 7.8%; +Bay K 8644: +103 +/- 30% (% basal); p < 0.005) as well as Nif (2 Hz vs. 0.5 Hz:
  
  
  METHODS
  -8.8 +/- 9.7%; +Nif: +90.9 +/- 31.5% (% basal); p < 0.05), were able to restore a positive FFR in PAP. By measurement of tetanic tension and posttetanic potentiation in the presence of the 1,4-dihydropyridines, we support the hypothesis of the existence and functional relevance of a dihydropyridin-ryanodine receptor junctional complex. In skinned fiber preparations, Bay K 8644 showed no effect on Ca(2+)-sensitivity or caffeine induced Ca(2+)-release. Rya (10 microM) decreased force of contraction in PAP and was effective in restoring a positive FFR (2 Hz vs. 0.5 Hz:
  
  
  METHODS
  -7.3 +/- 5.1%; +Rya: +98.0 +/- 31.9% (% basal); p < 0.05). Thus, the altered FFR and Ca(2+)-homeostasis in failing human myocardium may result from changes in sarcolemmal Ca(2+)-influx and/or from altered SR-Ca(2+)-load.
authors.affiliation: Klinik III für Innere Medizin, Laboratory of Muscle Research and Molecular Cardiology, Köln.
authors.forename: H
authors.initials: H
authors.lastname: Reuter
authors.forename: C
authors.initials: C
authors.lastname: Zobel
authors.forename: K
authors.initials: K
authors.lastname: Brixius
authors.forename: B
authors.initials: B
authors.lastname: Bölck
authors.forename: R H
authors.initials: RH
authors.lastname: Schwinger
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000328:Adult; D000368:Aged; D002118:Calcium / Q000502:physiology*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D008875:Middle Aged; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D016276:Ventricular Function
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; D002118:Calcium