Formation of reactive oxygen species at increased contraction frequency in rat cardiomyocytes.
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.
Heinzel
Frank R
FR
Institut für Pathophysiologie, Universitätsklinikum Essen, Hufelandstrasse 55, 45122 Essen, Germany.
Luo
Yukun
Y
Dodoni
Giuliano
G
Boengler
Kerstin
K
Petrat
Frank
F
Di Lisa
Fabio
F
de Groot
Herbert
H
Schulz
Rainer
R
Heusch
Gerd
G
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
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