title: K201 improves aspects of the contractile performance of human failing myocardium via reduction in Ca2+ leak from the sarcoplasmic reticulum.
abstract: In heart failure, intracellular Ca2+ leak from cardiac ryanodine receptors (RyR2s) leads to a loss of Ca2+ from the sarcoplasmic reticulum (SR) potentially contributing to decreased function. Experimental data suggest that the 1,4-benzothiazepine K201 (JTV-519) may stabilise RyR2s and thereby reduce detrimental intracellular Ca2+ leak. Whether K201 exerts beneficial effects in human failing myocardium is unknown. Therefore, we have studied the effects of K201 on muscle preparations from failing human hearts. K201 (0.3 microM; extracellular [Ca2+]e 1.25 mM) showed no effects on contractile function and micromolar concentrations resulted in negative inotropic effects (K201 1 microM; developed tension -9.8 +/- 2.5% compared to control group; P < 0.05). Interestingly, K201 (0.3 microM) increased the post-rest potentiation (PRP) of failing myocardium after 120 s, indicating an increased SR Ca2+ load. At high [Ca2+]e concentrations (5 mmol/L), K201 increased PRP already at shorter rest intervals (30 s). Strikingly, treatment with K201 (0.3 microM) prevented diastolic dysfunction (diastolic tension at 5 mmol/L [Ca2+]e normalised to 1 mmol/L [Ca2+]e: control 1.26 +/- 0.06, K201 1.01 +/- 0.03, P < 0.01). In addition at high [Ca2+]e) K201 (0.3 microM) treatment significantly improved systolic function [developed tension +27 +/- 8% (K201 vs. control); P < 0.05]. The beneficial effects on diastolic and systolic functions occurred throughout the physiological frequency range of the human heart rate from 1 to 3 Hz. Upon elevated intracellular Ca2+ concentration, systolic and diastolic contractile functions of terminally failing human myocardium are improved by K201.
authors.affiliation: Abteilung Kardiologie und Pneumologie, Georg-August-Universität, Göttingen, Germany. ktoischer@med.uni-goettingen.de
authors.forename: Karl
authors.initials: K
authors.lastname: Toischer
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Lehnart
authors.forename: Gero
authors.initials: G
authors.lastname: Tenderich
authors.forename: Hendrik
authors.initials: H
authors.lastname: Milting
authors.forename: Reiner
authors.initials: R
authors.lastname: Körfer
authors.forename: Jan D
authors.initials: JD
authors.lastname: Schmitto
authors.forename: Friedrich A
authors.initials: FA
authors.lastname: Schöndube
authors.forename: Noboru
authors.initials: N
authors.lastname: Kaneko
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Loughrey
authors.forename: Godfrey L
authors.initials: GL
authors.lastname: Smith
authors.forename: Gerd
authors.initials: G
authors.lastname: Hasenfuss
authors.forename: Tim
authors.initials: T
authors.lastname: Seidler
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D006333:Heart Failure / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000187:drug effects*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D013841:Thiazepines / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D013841:Thiazepines; C109183:K201 compound; D002118:Calcium