title: Formation of reactive oxygen species at increased contraction frequency in rat cardiomyocytes.
abstract: OBJECTIVE
  Reactive oxygen species (ROS) play an ambivalent role in cardiomyocytes: low concentrations are involved in cellular signaling, while higher concentrations contribute to cellular injury. We studied ROS formation during increases in contraction frequency in isolated cardiomyocytes.
  
  
  METHODS
  Rat ventricular cardiomyocytes were loaded with dichlorodihydrofluorescein and electrically stimulated (37 degrees C). ROS formation was assessed by the rate of oxidation-dependent fluorescence increase (OxR). Oxygen consumption (VO(2)) and NAD(P)H autofluorescence were measured in parallel experiments.
  
  
  RESULTS
  Increases in contraction frequency were accompanied by an increase in VO(2) and a decrease in NAD(P)H fluorescence. OxR increased to 124+/-4%, 146+/-8%, 204+/-25% and 256+/-29% of OxR at baseline during 1, 2, 3 and 4 Hz stimulation, and subsequently returned to baseline values with 0.2 Hz. The OxR increase was dose-dependently inhibited by the antioxidant NAC (10 and 100 mM), but unaffected by the NO synthase inhibitor l-NAME (200 microM and 10 mM). The OxR increase was attenuated when myosin ATPase activity was inhibited by butanedione monoxime (BDM; 5 mM).
  
  
  CONCLUSIONS
  Increased contraction frequency induces ROS formation in rat cardiomyocytes.
authors.affiliation: Institut für Pathophysiologie, Universitätsklinikum Essen, Hufelandstrasse 55, 45122 Essen, Germany.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Heinzel
authors.forename: Yukun
authors.initials: Y
authors.lastname: Luo
authors.forename: Giuliano
authors.initials: G
authors.lastname: Dodoni
authors.forename: Kerstin
authors.initials: K
authors.lastname: Boengler
authors.forename: Frank
authors.initials: F
authors.lastname: Petrat
authors.forename: Fabio
authors.initials: F
authors.lastname: Di Lisa
authors.forename: Herbert
authors.initials: H
authors.lastname: de Groot
authors.forename: Rainer
authors.initials: R
authors.lastname: Schulz
authors.forename: Gerd
authors.initials: G
authors.lastname: Heusch
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008929:Mitochondria, Heart / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009218:Myosins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D013481:Superoxides; C004717:diacetylmonoxime; D019001:Nitric Oxide Synthase; D019255:NADPH Oxidases; D009218:Myosins; D003931:Diacetyl; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine