title: [Effect of changed extracellular K(+) and Mg(2+)-concentration on intracellular Ca(2+) homeostasis, contraction coupling and force-frequency relations in the human myocardium].
abstract: The intracellular Ca(2+)-homeostasis may be affected by changes of the extracellular K(+)- and/or Mg(2+)-concentrations. Mg2+ reduces the Ca(2+)-influx via L-type Ca(2+)-channels, facilitates Ca(2+)-uptake into the sarcoplasmic reticulum, modulates the Ca(2+)-induced Ca(2+)-release and the Ca(2+)-binding to troponin C. The extracellular K+ activates the Na+/K(+)-ATPase and changes the membrane potential thereby affecting the mode of action of the Na+/Ca(2+)-exchanger. Especially when intracellular Ca2+ regulation is altered, for example in heart failure, Mg2+ and K+ exert beneficial effects on the frequency-dependent force-generation in human myocardium. Thus, extracellular Mg2+ and K+ influence contraction coupling in the human myocardium.
authors.affiliation: Klinik III für Innere Medizin, Universität Köln.
authors.forename: R H
authors.initials: RH
authors.lastname: Schwinger
authors.forename: K
authors.initials: K
authors.lastname: Frank
authors.forename: S
authors.initials: S
authors.lastname: Hoischen
authors.forename: J
authors.initials: J
authors.lastname: Müller-Ehmsen
authors.forename: K
authors.initials: K
authors.lastname: Brixius
mesh_terms: D000328:Adult; D000368:Aged; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000502:physiology; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology; D001026:Coronary Artery Bypass; D003326:Coronary Circulation / Q000502:physiology; D003331:Coronary Vessels / Q000503:physiopathology; D046508:Culture Techniques; D005110:Extracellular Space / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D016027:Heart Transplantation; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007424:Intracellular Fluid / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*
chemical_list: D000252:Calcium-Transporting ATPases; D008274:Magnesium; D011188:Potassium; D002118:Calcium